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COPYRIGHT DEPOSre 



NOTES 



ON 



HEATING AND VENTILATION 



BY 



JOHN R. ALLEN 

JUNIOR PROFESSOR MECHANICAL ENGINEERING 
UNIVERSITY OF MICHIGAN 

MEMBER AMERICAN SOCIETY MECHANICAL 
ENGINEERS 



DOMESTIC ENGINEERING 

58-64 North Jefferson Street 

CHICAGO 

1905 



LIBRARY of CONGRESS 
Two Copies Recefvtd 

APR 13 !906 



>/\ Copyright Entry 
CLASS CC XXc. No 



COPY B. 




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COPYRIGHT 

DOMESTIC ENGINEERING 

19 05 



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Preface 

The chapters comprising this book are a brief resume 
of the lectures delivered by the author to the classes in 
heating and ventilation at the University of Michigan. 
The subject matter was first published as a series of 
articles in Domestic Engineering. 

The book has been written primarily for the steam- 
fitter and designer of heating systems. It presupposes 
a knowledge of the construction and operation of the 
simpler forms of heating systems and has been reduced 
to as brief a form as possible so that the reader can 
readily find the notes or data desired. 

The design of heating and ventilating systems has 
not been reduced to an exact science. The factor of 
judgment and experience in designing heating plants is 
a large one. One reason for this is the lack of exact 
experimental data governing some of the most important 
factors entering into these calculations. This lack must 
be filled from the designer's experience. 

The tables of heat losses from radiating surfaces and 
the tests of pipe coverings have been compiled from the 
results obtained from the experiments made under the 
direction of Prof. M. E. Cooley, Dean of the Departnjent 
of Engineering, University of Michigan. The author also 
has shown illustrations of tunnel sections which have 
been used by Prof. Cooley in the design of a number of 
central heating systems. John R. Allen. 

Ann Arbor, October 30, 1905. 



TABLE OF CONTENTS 

PAGE 

INTEODUCTION. 
Theory of heat and measurement of temperature .... 9 

CHAPTEE I. 

Heat losses from buildings and rules for determining the 
heat losses in different constructions 13 

CHAFTEE II. 
Different forms of heating systems; their advantages, 
disadvantage and relative economy 27 

CHAPTEE III. 
The design of a direct steam heating system and the 
properties of steam 37 

CHAPTEE IV. 
Design of an indirect steam heating system 59 

CHAPTEE V. 
Steam boilers and steam piping. Determination of size 
and details of construction 69 

CHAPTEE VI. 
Ventilation and the pollution of air by human beings, 
artificial lighting and chemical processes 91 

CHAPTEE VII. 
Heating systems designed with reference to ventilation. 
Design of hot air furnace and fan system of venti- 
lation 99 

CHAPTEE VIII. 

Central heating systems; their design and installation, 
with discussion of different methods of carrying 
pipes underground 131 

CHAPTEE IX. 
Pipe coverings, pipe, valves, temperature regulation, air 
washing and exhaust heating 145 



SUBJECT INDEX. 



Page. 
A 
Absolute temperature.. 10 
Air changes of, for ven- 
tilation 95 

dilution of, for dif- 
ferent chemicals.. 94 

flues 99, 105-106 

mixing systems 124 

moisting of, for hot 

air furnaces 104 

pollution of 92-93 

valves 148 

washers 151 

Anchors for steam pipe 143 

B 

Boilers for central heat- 
ing system 132 

cast iron, proportions 

of 72 

horse power of 72 

proportions of 71 

types of 69 

Brick walls, heat less 

through 22 

Buildings, determina- 
tion of heat loss 

from 22 

example of heat loss 

from 26 

loss of heat from. . . 13 

materials, loss from 

different kinds. ... 22 

rules for loss of heat 

from 13 



Carbon dioxide, amount 

allowable 96 

Cast iron boilers, pro- 
portions of 72 

Ceilings, heat losses 

from 22 

Central heating system, 

boilers for 132 

combined with power 135 

design and location 131 

high pressure 134 

low press, pump re- 
turn 135 

piping for 133 

tunnels for 139 

size "of pipes 140 

Cold air ducts 105 

Conduction, example of 17, 18 



Page. 

Connections, calculation 

of loss by 18, 20 

Connections for radi- 
ators 89 

Coverings for pipe.... 145 



Dampers for hot air 

flues 106 

Dams in return pipes.. 74 
Direct steam heating, . 

30, 41. 50, 53 

Disc fans 126, 129 

Doors, heat loss from. 22 

Drainage of steam pipes 85 

Drip pipes 73 

Ducts, cold air 105 

for underground pip- 
ing 137 

for fans system, ven- 
tilation 122 

recirculating 105 

E 

Economy of different 

heat systems 34 

Example, direct steam 

heating 53 

direct steam heating 

table for 54 

fan heating system. . 128 

heat loss by conduc- 
tion 18 

heat loss by radia- 
tion 16 

heat loss from build- 
ings 26 

hot air heating 110 

hot air heating table 

for 110 

size of steam mains. 82 

of specific heat 11 

Exhaust steam heating. 149 

steam and hot water 

combined 152 

Expansion of steam 

pipes 85 



Factors for exposure.. 21 

Fahrenheit temperature 9 

Fan coils 119, 120 

Fans, disc 126, 127 

Fan heaters, dimensions 

of 122 



Page. 
Fan heaters, 

steel plate efficiency 

varying pressure. . 117 

size, speed, etc 115 

systems 

32, 34, 111, 114, 122, 128 

Fittings 149 

Floors, heat loss from. 22 

Flues, foul air 107 

friction in table of. . 124 

hot air 106 

proportions of . . . . 107 

materials for 126 

recirculating 105 

size of, for indirect 

radiators 64 

Flue radiators, heat 

losses, table of. . . . 46 

Foul air flues 107 

Furnace hot air sys- 
tem 29-109 

G 

Grates 27 

Gravity system of pip- 
ing 80 

H 

Hangers for pipe 143 

Heat given off by hu- 
man beings 95 

illuminants 94 

loss from buildings.. 

13, 22, 26 

by connection 18 

from exposure 21 

effect of height of 

room on 20 

from radiators direct 41 

indirect 60 

flue 46 

from fan heater coilsll9, 120 

from pipe covering. . 146 

nature of 9 

specific 11 

relation to work. ... 10 

unit of 10 

Heater coils for fan 

system 119-122 

Heating apparatus 

classified 27 

by direct steam 30 

indirect steam 31 

hot water 32 

fan system 32 

hot air 103 

High pressure heating. 134 
Horsepower of steam 

boiler 72 



Page. 
Horsepower 

to drive steel plate 

blower 115 

Hot air heating flues. .106, 107 

furnace 29, 103, 109 

system 103, 108, 109 

example of 110 

Hot water system. .31, 32, 152 
Human beings, heat 

given off by 95 

Humidity 104, 151 



Indirect steam heat- 
ing 64, 65 

steam radiators. . .59, 60, 64 



Location of mains and 

risers 88 

Lighting, pollution of 

air by 93 

heat given off by. . . . 94 

M 

Mains, location of 88 

return 73, 84 

steam 73, 81, 82, 83 

Moistening of air. .. .104, 151 



O 

Overhead steam mains 



79 



Pipe covering 145, 146, 147 

Pipes, expansion of.... 85 

Piping, hangers and 

anchors for 90, 143 

sizes for central heat- 
ing 133, 140 

for steam 73, 

75, 77, 78. 79, 80, 85, 149 

protection of 88 

underground systems 

of 137 

Pitch of steam piping. 73 
Pollution of air in ven- 
tilation 93 

Products of respiration 92 

R 

Radiation, loss by 14 

Radiators, direct steam 

41, 42, 47, 49, 50 

flue 46 

indirect steam 

59, 60, 61, 64, 65, 66 

connection of 89 

relative efficiency of 

different types ... 42 



Page. 
Registers, location of . . 99 
Regulation of tempera- 
ture 151 

Reliefs 73 

Return system 73 

mains, table of size 

of 84 

Resistance of air flues. 124 

Risers 73, 88 

Rules for heat loss from 

buildings 23 

for direct steam heat- 
ing 50 

for indirect steam 

heating 65 

for hot air heating. . 109 
for size of steam 

mains 83 

S 
Siphon in steam main. 74 

Skylights, heat loss 

from 22 

Specific heat 11 

Steam boilers 69, 71, 72 

Steam heating, diregt. . 

30, 34, 50, 53 

indirect 31, 65 

exhaust 149 

mains 73, 81, 82, 83 

piping. . . 73, 75, 77,78, 79, 85 
Steam radiators, direct 

41, 42,47, 49 

flue 46 

indirect 59, 60, 63, 65 

Steam traps 74 

Steel plate blowers 115, 116 

Supporting steam pipe . 90 

T 

Tables — 

Air dilution for 
different chemi- 
cals 94 

Changes of air for 

ventilation .... 96 

Conducting power. 17 

Heat losses from 
direct radiators. 41 

Heat losses from in- 
direct radiators. 64 

Heat losses from 

pipe covering.. .146, 147 

Heat losses for 
building mate- 
rials 22 

Product of respira- 
tion from human 
beings 92 



Page. 

Tables 

Hot air system. .108, 110 
Product of combus- 
tion from light- 
ing systems .... 93 
Properties of 

steam 38 

Proportions of cast 

iron boilers 72 

Radiating power . . 14 

Resistance of air 

flues 124 

Speed capacity etc. 
of steel plate 

fans 116, 117 

Speed capacity etc. 

of disc fans. ...126, 129 

Specific heat 11 

Size of flues for in- 
direct radiators.. 64 
Size of steam and 

return mains ... 84 

Steam heating ex- 
ample, direct. . . 54 
Steam heating ex- 
ample, indirect.. 66 
Temperature of air 
leaving indirect 

radiator 61 

Temperature, Fahren- 
heit 9 

absolute 10 

assumed in rooms. . . 25 

average for year .... 25 

air leaving hot air 

furnace 61 

regulation 151 

Traps, steam 74 

Tunnels 139, 143 

V 

Valves 87, 149 

air 148 

Vacuum heating sys- 
tem 150 

Ventilation 

91, 95, 96, 97, 99, 122 

W 

Water hammer 74 

line in heating sys- 
tem 74 

seals 74 

Windows, heat losses 

from 22 

Wooden houses, losses 

from 22 

Work, relation to heat. 10 



NOTES ON HEATING AND 
VENTILATION 



IN TR O D U C TI O N, 

HEAT. 

Iloat is a form of motion. The modern scientific concep- 
tk'n of heat is that it is produced by the motion of the 
particles of matter which compose 
any body. All matter is conceived as Heat, 

being made up of small particles 

called molecules. These' particles do not exist in a state of 
rest, but are in constant vibration. If these particles move 
slowly the body is at a low temperature; if they move 
mere rapidly the body is at a higher temperature, the 
temperature of the body being determined by the rapidity 
of the motion of the particles. In measuring heat there 
are two properties to be considered — the intensity and 
the quantity. This may be compared to measuring water 
in a pipe. We measure the pressure of the water in the 
pipe by means of a gauge in pounds per square inch. The 
quantity of water is measured in pounds. In the same 
way the intensity of heat is measured by the thermometer 
in degrees and the quantity of heat is measured by com- 
parison with the quantity of heat which a pound of water 
will absorb. 

Temperature, which is a measure of the intensity of the 
heat of a body, might also be considered as measuring 
the velocity of the molecules of the 
body. In mechanical engineering all Temperature. 
measurements of temperature are 

made on the Fahrenheit scale. On this scale the 
freezing point is taken at 32° and the boiling point a? 



10 xN'oTES ON Heating and Ventilation 

212", the tube of the thermometer between these points 
being divided into 180 equal parts called degrees. 

We never know the total amount of heat in a body. 
As it is impossible to bring any body to a condition of 
absolutely no heat; the heat in any body must always be 
measured from some assumed zero point and in the Fah- 
renheit scale this assumed zero point is 32° below the 
freezing point. For theoretical purposes, however, it is 
highly desirable to have some absolute standard of 
heat. A perfect gas at 32° contracts about 1/493 of its 
volume for each degree Fahrenheit that it is reduced in 
temperature. If, then, we keep on decreasing the tem- 
perature of a perfect gas from 32°, until it reaches a point 
493° below the 32° Fahrenheit, it would have, theoretic- 
ally, no volume. If it has no volume, the amount of heat 
which it contains must be zero. This point, then, is called 
the absolute zero. This point is manifestly an ideal one. 
To find the absolute temperature in degrees it is neces- 
sary to add to the Fahrenheit temperature 461 degrees, 
that is, 32° Fahrenheit corresponds to 493° absolute. 

Heat is not a substance and it can not be measured as 
we vrould measure water in pounds or cubic feet, but it 

must be measured by the effect which 

Uiiit of Heat. it produces. Suppose it requires a 
certain amount of heat to raise a 
pound of water from 39° to 40° Fahrenheit. It would 
require three times that quantity of heat to raise a pound 
of\-ater from 39° to 42° Fahrenheit, The heat re- 
quired to raise a pound of water one degree Fahrenheit is 
called a British thermal unit, and is designated by let- 
ters B. T. U. 

Work is measured in foot-pounds. The unit of work 
is the work required to raise one pound Ihrough a 

height of one foot. Ten units of 
Kelation Between work or ten foot-pounds would be 

Heat and Work, the amount of work done in raising 

ten pounds one foot high or one 

pound ten feet high. As heat is a form of motion, there 



Notes on Heating and Ventilation ii 

must be some definite relation between heat and work. 
This relation was first determined by Joule. By a series 
of experiments Joule found that one heat unit was equi- 
valent to 778 foot-pounds. It is possible then to express 
heat either in heat units or in foot-pounds. 

Different substances require very different quantities of 
heat to produce the same change of temperature for the 
the same weight. As for example, 
to raise one pound of water one de- Specific Keat. 
gree requires one B. T. U.; to raise 

one pound of ice one degree requires .504 B. T. U. 's ; to 
raise one pound of wrought iron one degree requires .219 
B. T. U. The heat necessary to raise one pound of a 
substance one degree, the heat being expressed in British 
thermal units, is called specific heat. The following table 
gives the specific heat of the principal substances which 
we meet with in engineering work: 



Table 1.- 


—Specific 


Heat. 




SUB STANCE 






B. t. u. 


Water 






. 1 

.504 

.194 

.1298 

.1165 

.1138 

.0951 

.0939 

.056-2 

.0314 


Ice 






Glass 






Cast iron 






Soft steel 

Wroii'^'lit iron . . . 






CoDper 






Brass 






Tin 






Lead . . 













It is required to raise the temperature of a cast iron 
radiator weighing 300 pounds from 70° to 212°. The 
temperature through which the iron 
would be raised would then be 212 Example. 

minus 70° or 142°. Prom the table 

we see that it would require to raise one pound of cast 
iron one degree .1298 heat units, then to raise one pound 
142° would require 142 times .1298 or 18.43 heat units 
and to raise 300 pounds one degree would require 300 



12 Notes on Heating and Ventilation 

times this amount or 5,529 B. T. U. 's, the heat required 
to heat the radiator. 

In solid substances the change in volume when they 
are heated is so small that it is not considered. In gases, 
however, the change in volume when the gas is heated 
without being confined, depends directly upon the absolute 
temperature and may be very large. AVhen air is confined 
and is heated, it cannot expand; if it does not expand 
there is no work done because, from our definition of 
work, it is necessary when work is done, that the body 
have some movement. On the other hand, when air re- 
ceives heat and is free to expand it does work. For in- 
stance, if air were confined in a cylinder by a piston, and 
this air were heated, the air would expand and the piston 
would be moved out. As the piston is moved through 
a certain space there must be work done. On the other 
hand if the piston were blocked so that it could not move, 
then the air on being heated would do no work. Then in 
these two cases different amounts of heat will be re- 
quired to raise the substance one degree, depending upon 
whether there is external work done or not. 

It is necessary in gases that we consider two 
specific heats, the specific heat of constant volume and 
the specific heat of constant pressure. For air the specific 
heat of constant volume is .1689, for constant pressure it is 
.2375. It is seldom that we use air in a confined space, 
so that, so far as this work is concerned, we shall in most 
cases consider the specific heat of air as .2375, that is, 
to raise one pound of air one degree requires .2375 B. T. U. 



CHAPTER I. 



HEAT LOSS FROM BUILDINGS. 

Heat is lost from a room in three ways — by the direct 
transmission of the heat through the walls and windows; 
by tbe passage of air up the foul air 
flues, and by the filtration of air Loss of Heat 
through the walls. The first two From Buildings, 
losses are easily determined, but the 

determination of the loss by filtration must always involve 
a large factor of judgment and experience. 

All building construction is more or less porous. This 
is well exemplified by the old experiment made with a 
common brick. Two cornucopias of paper are pasted on 
opposite sides of a common brick, the large end of the 
cornucopias being fastened to the brick. Opposite the 
small end of the cornucopia at one side is placed a 
lighted candle. By blowing into the cornucopia on the 
opposite side, the candle may be blown out, the air 
having passed directly through the brick. 

The experiments which have been made in order to de- 
termine this loss generally tend to show that in the or- 
dinary well-constructed building the air in the room will 
change about once per hour, when all doors and windows 
are closed. 

In order to study the other heat losses from a room it 
will be necessary to study the laws of cooling. A body 
may be cooled in three different ways — by radiation, by 
conduction and by convection, (contact of air). In or- 
der to understand this more thoroughly, it will 
be necessary to take up each of these losses separately. 

The heat that passes from a body by radiation may 



14 



Notes on Heating and Ventilation 



be considered similar to the light which is given off by 

a lamp. There is alvrays a transfer 
Radiation. of radiant heat from the body of a 

higher temperature to the body of 
lower temperature. The amount of heat radiated will de- 
pend upon the difference in temperature between the bodies 
and the substance through which this heat passes. 

The losses by radiation may be better understood hy 
referring to Fig. 1. Suppose the plate PP to be of cast 
iron 1 foot square and 1 inch thick. Let us suppose this 
plate to be on both sides at a temperature of 60°. Let 
this plate form one side of a room, the walls WWW be- 
ing non-conducting substances and at a temxperature of 
59°, the air in this space being at a temperature of 
60°. Since the walls and the air in the space are at 
the same temperature, there will be no less of heat from 
the air to the v/alls, but all the heat that passes from 
the plate PP to the walls must pass by radiation. For 
ordinary temperatures of heating surfaces, say 60 or 70°, 
the loss by radiation will equal the difference in tem- 
perature between the hot body and the cold body multi- 
plied by a factor representing the radiating power of 
the body. The following table gives the radiating powei 
of diff^erent substances: 



Table II — Radiating Power. 

Radiating power of bodies, expressed in heat units, 
given off per square foot per hour for a difference of 
one degree Fahrenheit. (Peclet.) 

Copper, polished 0327 

Iron, sheet 0920 

Glass 594 

Cast ir.on. rusted 648 

Building stone, plaster,- wood, brick 7358 

Woolen stuffs, anj^ color 7522 

\Tater 1.085 



Heat is radiated in straight lines exactly as light is 
given off from the source of light. We may have heat 
shadows the same as we have light shadows and the 



Notes on He.\ting and Ventilation 



15 



intensity of the heat is proportional to the square of the 
distance from the source. Some bodies are transparent 
to heat and other bodies absorb heat, the same as some 
bodies are transparent to light and others absorb light. 




Figure 1. 

The transparency of bodies to heat is called diather- 
mancy. Gases, such as air, oxygen, nitrogen, and hydro- 
gen, are almost perfectly transparent to heat, while 
wood, hair, felt and other non-conducting bodies are 
almost perfectly opaque to the transmission of heat. The 
loss of heat by radiation is independent of the form of 
a body so long as it does not radiate heat to itself. The 
color or condition of the surface of different bodies 



16 



Notes on Heating and Ventilation 



affects their radiant power. Smoothly polished surfaces 
radiate less heat than rough surfaces. As, for instance, 
a surface painted with lamp black will radiate over 13 
times as much heat as a polished copper surface. 




Suppose we have a glass surface ^ve square feet in 
area. The glass surface is at a temperature of 70° and 

the objects surrounding it are at a 

Example temperature of zero. From the table 

we see that one square foot of glass 

(surface) loses .594 heat units in an hour for a difference 

of one degree between it and the surrounding objects. For 

a difference of 70°, then, each square foot of glass would 



Notes on Heating and Ventilation it 

lose 70 times that amount or 41.5 heat units and 5 square 
feet of glass would lose 5 times that amount or 207.5 
heat units per hour. 

The heat transmitted by conduction is the heat which 
is transmitted through the body itself. For example, 
take the condition shown in Fig. 2. 
PP is a plate, one side of which is Conduction, 

enclosed by the walls WW. Let the 

temperature of the plate outside be 59°, the temperature 
on the inside of the plate be 60°; the temperature of the 
walls be 60 degrees, the temperature of the air in the 
room be 60°. Then all the heat that is lost by the room 
must be lost by direct conduction through the plate PP. 
The amount of heat conducted will depend upon the ma- 
terial of which the conductor is composed and in addi- 
tion it will also depend upon the difference in tempera- 
ture between the two sides of the plate and upon the 
thickness of the plate. The conduction through any plate 
may be calculated as follows: Multiply the factor given 
in Table III by the difference in temperature between the 
two sides of the plate and divide the result by the thick- 
ness of the plate in inches. The quotient will be the heat 
transmitted by conduction per square foot of surface. 



Table III — Conducting Power. 



The conducting power of materials, expressed in the 
quantity of heat units transmitted per square foot per 
hour bj^ a plate one inch thick, the surfaces on the two 
sides lof the plate differinj? in temperature by one de- 
gree. (Peclet.) 

B. T. U's. 

Copper 515 

Iron 233 

Lead 113 

Stone 16.7 

Glass 6.6 

Brick work 4.8 

Plaster 3.8 

Pine wood .75 

Sheep's wool .323 



Suppose a boiler plate 5 feet square, i/{.-inch thick, 
to have a temperature of 70° on one side and a tempera- 



18 



Notes ox Heating and Ventilation 



ture oil the opposite of 200°. The 
Example difference in temperature of the two 

sides of the plate would be 130°. 
The amount of heat conducted would then be 233x130-!- 
1/2 — 15145 the heat transmitted per square foot of plate. 



^m%%>^w^%^;m%m%m%%m 




^ ea 






Air5S 






wmmmmmmmm^M'/xy, 



i 






figure 3. 

Then ^nq square feet would transmit ^yq^ times this 
amount or 75,725 B. T. U. 's in one hour. 

Loss by convection is sometimes termed loss by contact 
of air. Take, for example, the condition shown in Fig. 

3. Let P be a vertical plane of 
Convection. metal one foot square, having: its 

Surfaces maintained at 60° tempera- 
ture. Let the walls WW also be at a temperature 



Notes on Heating and Ventilation 



19 



of 60°. Let the air in the room be 59°. In this case there 
will be no loss of heat from the walls to the plate by 




70' 



70' 

Figure 4. 



radiation and there will be no loss through the plate by 
conduction, but heat will be transmitted from the walls 



20 Notes on Heating and Ventilation 

and the plate to the air of the room. The air which 
comes in contact with the warmer walls will be heated. 
As air is heated it becomes lighter and rises and a cur- 
rent is formed. This produces a circulation of air, and 
this circulation of air gives rise to a loss of heat by 
convection or contact of air. 

The loss of heat by convection is independent of the 
nature of the surface, wood, stone or iron losing the same 
quantity of heat, but it is affected by the form of the 
body, that is, a cylinder and a sphere would lose different 
amounts of heat per square foot. Take the steam radiator, 
for example. The air nearest the radiator becomes heated 
and rises; as it rises its place is taken by other colder 
air coming off the floor so that a current of air is estab- 
lished. In the ordinary type of radiator, the loss by con- 
tact of air represents about half the loss of heat, the bal- 
ance being lost by radiation. 

The calculation of the heat lost by convection is quite 
complicated and different expressions have been derived 

for this loss for different forms 
Calculation of of surfaces. Those developed by 
Convection Peclet are given in Box's treatise 

Losses. on Heat. 

The rules given for convection in 
the text-books on heat cannot, as a rule, be applied to 
the loss of heat from buildings. All these rules assume 
that the air surrounding the object is in a perfectly 
quiescent state. In buildings this is not the case, for the 
air surrounding a building is rapidly circulated by the 
winds. Theoretically a high building would lose pro- 
portionally less heat than a low building because in the 
upper stories there would be a smaller difference in tem- 
perature between the air inside the room and the air 
outside than in the lower stories. This, however, U not 
the case, as the wind circulates the air outside the build- 
ing and makes the temperature of the air surrounding 
the building on the outside practically the same at all 
levels. 



Notes on Heating and Ventilation 21 

Inside the room, however, the air at the top of the 
room is much warmer than that at the floor. The result 
is that the rate of transmission of heat in rooms with 
high ceilings is considerably higher than in rooms with 
low ceilings, as in the room with a high ceiling we have 
a greater difference of temperature between the inside 
and the outside air at the ceiling. This difference is not 
ordinarily considered unless the height of the room ex- 
ceeds ten feet. If the height of the room does not ex- 
ceed ten feet the temperature taken five feet above the 
floor line may be assumed as the average temperature in 
the room. 

The loss of heat from buildings was first investigated 
both experimentally and theoretically by Peclet. The 
greater part of his work is given in Box^s treatise on 
Heat. The results obtained by Peclet are difficult to 
apply practically and nearly all the rules that are used 
to determine the loss of heat from a building are largely 
empirical. The constants determined by the German 
government are probably the most reliable we have. 
They are given in the following table, the results being 
expressed in the heat units transmitted per square foot of 
surface per degree difference of temperature. 

It is found that the thickness of glass in the window 
makts very little difference in the heat transmission. In 
the table below double glass refers to two sheets of glass 
with an air space between, what is sometimes called double 
glazing. Where brick walls are made double with air 
space between the air space will reduce the loss of heat 
about 20 per cent below that given by a solid wall. 

The heat losses given in the following table should be 
increased as follows: Where the room has a north ex- 
posure and the winds are severe, add 
10 per cent. When the building is Factors for 

heated in the day time only and al- Exposure. 

lowed to cool during the night, add 

10 per cent. When the building is heated occasionally, for 
example a church, add from 40 to 50 per cent. Where 



22 Notes on Heating and Ventilation 

a room has a northerly exposure and is subjected to ex- 
tremely high winds, add 30 per cent. It is usually ad- 
visable to assume for unwarmed spaces, such as cellars 
and attics, a temperature of about 32°. For vesti- 
bules and entrances unheated, which are being fre- 
quently opened to the outer air a temperature of 20° 
may be assumed. 



Table IV — Heat Losses. 



Surface. B. T. U. per hour per sq. ft. per degree 

difference of temperature. 

Window, single glass 776 

Window, double glass 518 

Skylight, single glass 1.118 

Skylight, double glass , 621 

Brick wall 4 inches thick 68 

Brick wall 8 inches thick 46 

Brick wall 12 inches thick 32 

Brick wall 16 inches thick 26 

Brick wall 20 inches thick 23 

Outer doors 42 

Floors, wooden beams, planked 083 

Floors, fireproof, floored with wood .124 

Ceilings, wooden beams, planked 104 

Ceilings, fireproof construction 145 

Ordinary wooden house construction 1 



In determining the loss of heat from a building all sur- 
faces should be considered which have on the side op- 
posite the room a lower temperature 
Betermination of than the temperature in the room, 
the Loss of Heat If a room is situated over a portion 
From a Build- of the cellar which is not heated, the 
ing, loss of heat through the floor should 

be considered. If the room has over 
it an unheated attic the loss through the ceiling should 
be considered. The loss through the sides of a room 
which is surrounded by rooms at the same temperature 
may be neglected. Doors entering directly into a room 
are considered to lose the same amount of heat as the 
windows. 



Notes on Heating and V^entilation 23 

A common rule for the loss of heat from a building is 
that given by Professor R. C. Carpenter in his book on 
^^Heat and Ventilation.'' This rule 
is ^developed frojm the following Rules for Deter- 
consideration. Referring to Table mining the Loss 
IV., we notice that one square foot of Heat. 

of glass conducts approximately four 

times as much heat as a brick wall 20 inches thick. If, 
then, we divide the wall surface by 4, the result will give 
us the number of square feet of glass surface, which would 
lose the same quantity of heat. Adding to this the actual 
glass surface would give us the total equivalent glass sur- 
face. In addition to this heat transmitted through the 
walls we must add the heat which is lost by the air which 
passes directly through the walls themselves. It is as- 
sumed that for ordinary sized rooms the air in the room 
will be changed about once an hour, so that we must fig- 
ure on heating the entire air in the room about once 
per hour. One cubic foot of air weighs, approximately, 
1/13 of a pound. To raise a pound of air one degree re- 
quires .238 B. T. IT.-'s. Then to raise one cubic foot of 
air one degree would require .238xl/13=:.0183 B. T. U. 
or one heat unit will heat l-f-. 0183^=54.6 cubic feet, or 
in round numbers say 55. If, then, we divide the con- 
tents of a room by 55 we will have the heat lost by 
filtration through the walls. Adding these factors to- 
gether will give the total heat lost from the room. This 
rule may be expressed more concisely as follows: 

KuLE 1. — Divide the contents of the room by 55 ; add the 
glass surface and the luall surface divided hy 4. The sum 
will he the heat lost from the room per degree difference of 
temperature between the air in the room and the air out- 
side the room. Multiply this sum by the- difference in 
temperature between the air inside the room and that out- 
side of the room and the product tuill be the heat lost from 
the room. 

Let C represent the volume of the room, W the wall S7ir- 
face, G the glass surface and D the difference of tempera- 



24 Notes on Heating and Ventilation 

turc 'between the air outside and the air inside the room. 
The heat loss from the room per hour expressed in B. T. 

(Cn W \ 

-7^ -}- J^ q\ ^ where n is a factor 
55 4 / 

which depends upon the tightness of the room and varies 
in value from 1 — 3. For ordinary room n=:l, for corridors 
1.5, for vestibules ^ to 3. 

It is quite customary to assume the difference in tem- 
perature between the air in a room and the air outside to 
be 70°. Where the windows are poorly fitted or the 
house loosely built, the loss by filtration should be doubled 
and in halls where the doors are being opened and closed 
frequently this should be multiplied by three. 

There is one criticism on this method of figuring the 
heat lost in the room. The diffusion loss is assumed to 
depend upon the cubic contents of the room. This of 
course is manifestly not correct, as the diffusion loss oc- 
curs through the walls and windows and must depend 
upon the area of the walls and windows. The rule, how- 
ever, will work very well for rooms of average size, but 
where the rooms have excessive wall and window sur- 
faces or where the cubic contents of the room is large 
compared to the wall and window surfaces, this rule 
will give inconsistent results. The following rule seems 
to the author to be capable of a much wider application: 
Rule 2. — Divide the wall surface by 4; add the glass 
surface; multiply this sum by the difference in tempera- 
ture between the air in the room and the air outside^ and 
then multiply the result by IV2, J^^is rule is for a well 
constructed building. If the building is old and poorly 
built, then instead of multiplying by 1% i^e result sliould 
be multiplied by 2; entrance halls midtiplied by ^Va* 

Or let W represent the wall surface, G the glass surface 
and d the difference of temperature between the air out- 
mde and the air inside the room. Then the heat loss from 
the room per hour expressed in B. T. U.^s would be 

I |_ (7 fdHy wlicre n is a factor which depends 



Notes on Heating and Ventilation 25 

upon the construction of the house or location of the room 
and varies in value from 1.5 to 2,5 as stated above. 

In figuring the radiating surface for any room the cubic 
contents should always be taken into consideration. In 
a large room with a small exposed wall surface, if only 
enough radiation is put in to cover the loss from walls and 
windows, the room will be slow to heat. In addition to 
taking care of the loss from walls and windows it is 
necessary for the radiator to heat the air in the room 
itself. In order to do this a large proportion of this air 
must either pass through the heating device or be carried 
out by the ventilating flues, so that where the cubic 
contents of a room is large it is advisable to add from 10 
to 20 per cent to the radiating surface to allow for the 
heating of the air in the room itself. The above re- 
mark applies only when the building is intermittently 
heated; when the building is continuously heated it is not 
necessary to consider the volume of the room. 

The following temperatures are usually assumed in de- 
termining the heat losses: 



Table V — Temperatures Assumed in Heating. 

Degrees 

Temperature of the outside air 

Temperature of stores 68 

Temperature of residences 70 

Temperature of halls and auditoriums 64 

Temperature of prisons 68 

Temperature of factories .60 to 66 

Temperature of cellars not warmed 32 

Temperature of attics not warmed 32 

Temperature of outside entrances 20 



The average temperature for the period of the year dur- 
ing which buildings are heated throughout the central 
states may be assumed to be approximately 35°. 

The following examples will show the method to be 
pursued in determining the heat lost from a building. 

Suppose a room, as shown in Fig. 4. Let the tempera- 



26 Notes on Heating and Ventilation 

ture be maintained in the room at 70 degrees, 

the temperature of the outside air 
Example 1. be 0. Let the walls be of brick 
8 inches thick, plastered on the in- 
side, the windows be 2%x6 feet; the ceiling of the 
room be 10 feet high. Let the room be on the second 
floor of the building, the rooms above and below heated. 
The window surfaces are 2x21/^x6=30 square feet. The 
total wall surface is 20x10=200 square feet. The net 
wall surface is 200 — 30=::170 square feet. Then the heat 
lost from the room per degree difference of temperature 
by rule 2, would be 170-^4+30=72%. As the difference 
between the outside and inside temperature is 70°, the 
.total heat lost is 72y2x70=5075 B. T. U. per hour. 

Take the same room as in Example 1, except that the 
room is covered by a flat tin roof. The air space between 

the ceiling of the room and roof 
Example 2. should be assumed to be at a tem- 
perature of 32°. Then, in addition 
to the loss figured in Example 1, there will have to be 
added the loss due to the tin roof. The area of the ceil- 
ing of the room would be 14x20=280 square feet. Ee- 
ferring to Table IV., we find the loss per hour through 
ceilings of wooden construction to be .104 B. T. U.'s per 
degree difference of temperature; then the loss through 
this ceiling would be, per degree of temperature, .104x280= 
29.1 B. T. U.'s. The room being at 70° and the attic 
space 32°, the difference in temperature would be 70 — 32= 
38 degrees. The total loss through the ceiling would then 
be 29.1x36=1047.6 B. T. U.'s. Adding this to the loss 
found in Example 1, we have a total loss from the room, 
5,075+1,047=6,122 B. T. U's. 



CHAPTER II. 



DIFFERENT FORMS OF HEATING. 

The different heating systems may be classed under 

two general heads — Direct and Indirect. In direct heat- 

ine the heating surfaces are placed _, .« ,. « „ ^ 
. ^^, T V. x^ . n £ Classification of Heat- 

in the rooms to be heated, as for . 

instance, stoves, steam radiators or ^ ^^ rams, 

hot water radiators. In indirect heating systems the heat- 
ing apparatus is usually placed in some other Toom and 
the heat carried to the room to be heated by means of 
pipes. Under this head would be included hot air fur- 
naces and the various systems of heating in which fresh 
cold air is made to pass over steam or hot water radiators 
on its way to the room. 

The indirect systems of heating naturally divide them- 
selves into two other classes, those using natural draft 
and those using forced draft. A good example of natural 
draft indirect heating is the hot air furnace, where the 
circulation of air through the house is produced by the 
difference in temperature between the air in the hot air 
flues and the cold air outside the flues. The fan systems 
of heating, used in heating school buildings and churches, 
are good examples of the forced draft system. In this 
case the draft is largely produced by mechanical means, 
usually a disc fan or a pressure blower. 

In order to understand better a discussion of the vari- 
ous forms of heating which will come later, it is desir- 
able to understand in general the advantages and dis- 
advantages of the various forms of heating. 

The most primitive form of heating apparatus is the 
grate. In the grate the air which passes through the fire 
and is heated by the fire all passes 
up the chimney and only the heat Grates, 

given off by radiation to the walls 
and objects in the room is effective in heating the room. 



28 Notes on Heating and Ventilation 

In grates of better construction this is somewhat im- 
proved by surrounding the grate by fire brick so arranged 
that the brick will become highly heated and radiate heat to 
the room. But the fact that all the air heated by the grate 
passes up the stack makes this a very uneconomical form 
of heating. In the best form of open grates only about 20 
per cent of the heat of the fuel is effective in heating the 
room. This form of heating, however, has been defended 
by many. It is a very popular form of heating throughout 
England and Scotland. The feeling of a grate-heated 
room is quite different from that of a room heated by 
other systems. All the heat is given off by radi- 
ation and the air in a grate-heated room is at a consid- 
erably lower temperature than the objects and persons in 
the room, owing to the fact that radiated heat does not 
heat the air through which' it passes. The air of the 
room being at a lower temperature its capacity for mois- 
ture is not increased as much as it would be were the 
air heated to a higher temperature. The result is that 
the air contains proportionally more moisture than is the 
case in other forms of heating. This, no doubt, is an 
advantage. On the other hand, it is impossible to heat 
the room uniformly and a person is hot or cold depend- 
ing upon his distance from the grate. Heating by means 
of grates is practiced only in the more moderate climates. 
The grate is useful in houses heated by other -^orms 
of heating as it serves as a most efficient foul air flue. 
The introduction of a large number of grates into a house 
adds materially to the ease with which the house may be 
ventilated. 

The stove is a marked improvement over the grate as a 
form of heating, particularly from the standpoint of econ- 
omy. The modern base-burner 
Stoves. stove is one of the most economic 

and efficient forms of heating, mak- 
irg use of from 70 to 80 per cent of the heat in the 
fuel. In heating by a stove the heat is given off both 
by radiation and by convection. The hot ^irface of the 
stove being at a higher temperature than the surround- 



Notes on Heating and Ventilation 29 

ing objects in the room radiates its heat directly to these 
objects. In addition the air surrounding the stove is 
heated and rises, passing along the ceiling to the cold 
wall and window surfaces where it is cooled, drops to 
the floor and passes along the floor back to the stove to 
be again heated. In selecting a stove to heat a given 
room care should be taken to select one of ample size so 
that only in the coldest w^eather would it be necessary to 
crowd it, that is, keep on the drafts, in order to heat 
the room. At the present time the stove as a general 
source of heat is being rapidly discarded because of the 
attendance required, the space occupied and the un- 
sightly appearance of the stove. Another serious objec- 
tion to the stove is the fact that it does not furnish 
ventilation to the room w^hich it heats. 

The hot air furnace is a natural outgrowth of the 
stove. In this system one large stove is placed in the 

basement of the building, the air __^. .. _.,^ 
X 1 ^ ,, . °j T Hot Air Fur- 

is taken from the outside, passed 

over the surfaces of the stove or 
furnace, carried up through the flues to the rooms to be 
heated. The principal advantage of the hot air furnace 
is that it provides a cheap method of furnishing both heat 
and ventilation, it requires little attendance and does not 
deteriorate rapidly when properly taken care of. The 
greatest disadvantage of this system is in the fact 
that the circulation of the heated air depends entirely 
upon natural draft, that is, it depends upon the differ- 
ence in weight between the air inside the flue and the 
air outside the flues. This difference of weight is ex- 
tremely small, so that the force producing circulation in 
the flue is always small. This force is easily overcome 
either by the winds or by the resistance of the piping. 
When a very strong wind blows against one side of the 
house it is difficult to heat the rooms on that side of 
the house. If the system is carefully designed, however, 
this diflSculty can be overcome in a measure. Another 
serious objection to the hot air furnace is that it is sel- 
dom dust tight and dust and ashes are carried into 



30 Notes on Heating and Ventilation 

the room. In general, however, the hot air furnace may be 
considered as a very good type of heating plant for 
small residences. 

In the case of the hot air furnace the heat is carried 
to the room by convection as all - -^at is carried from 
the furnace by the air which passes around the furnace and 
enters the rooms from the flues. This air circulates in the 
room and heats the objects and air in the room. The 
efficiency of the hot air system will vary, depending 
on the relative proportion of the air taken from outside 
and upon the temperature of the air entering the room. 
If the cold air entering the furnace is taken from the 
house itself and not from outside the efficiency of the 
hot air furnace will be almost the same as that of a 
steam furnace, that is, . from 70 to 75 per cent of the 
heat of the coal will go into the rooms. If, however, 
the cold air is taken from outside then the heat used 
in heating the air from the temperature of the outside air 
to the temperature of the room will be lost and under ordi- 
nary conditions of operation the efficiency would be from 
50 to 60 per cent. 

From the standpoint of ventilation direct steam heat 
would have little advantage over a stove, as it gives no 

steam Heating, '^'^'^' °^ supplying fresh air. Its 
_. . ' use m general should be confined to 
Direct. I,- 1, • T^^i 

rooms which require little or no 

ventilation. Mechanically, however, it has many advan- 
tages over the stove or the hot air furnace. The boiler 
for a building having this form of heating can be located 
anywhere in the basement, and the rooms are free from 
dirt or gas. The modern radiator is easily adapted to 
almost any location in the room, it is not affected by 
wind or local conditions and a distant room may be 
heated as easily as one close to the furnace. The effi- 
ciency of the direct steam-heating system is about the 
same as that of a stove and with a well-installed plant 
from 70 to 80 per cent of the heat of the fuel will be 
delivered by the radiator to the room. 



Notes on Heating and Ventilation 31 

The application of direct hot water radiators as a 
method of heating would be similar to that of steam, with 
the exception that the surfaces are at 
a much lower temperature and hence Hot Water Direct, 
more radiating surface will be re- 
quired. It has 2iil advantage over steam in that the 
temperature of the heating surface can be controlled 
easily, and can be anywhere from the temperature of the 
room to 200 degrees. In the steam radiator the surface 
is usually not less than 212 degrees. The principal dis- 
advantage of this system is in the fact that the circula- 
tion of the system is by natural circulation, that is, the 
circulation is produced by a difference in weight be- 
tween the water in the hot leg of the system and in the 
cold leg of the system. This difference in temperature 
is usually about 10°, so that the difference in weight be- 
tween these two columns of water is small and the re- 
sulting force producing circulation is of course small. 
It is necessary to be very careful in designing the 
piping for the hot water system, as the circulation may be 
easily affected by resistance of the pipe. In addition it 
will be affected by the height of the radiator above the 
boiler, the greater the height above the boiler, the greater 
will be the difference in weight between the two columns 
of water and the stronger will be the force producing cir- 
culation. This system in general requires more careful 
design and construction than the steam system. The ef- 
ficiency of the hot water system is practically the same as 
that of steam and we may expect to obtain in the room 
from 70 to 80 per cent of the heat in the coal. 

In heating witli indirect steam radiation cold air is 
drawn from the outside, passed through and around the 
hot radiator which is usually situated 
in the basement, and delivered by Indirect Steam 
pipes to the rooms to be heated. The Heating, 

rules governing the introduction of 

air into the rooms and the method of running pipes would 
be similar to that employed with hot air furnaces. The 



32 Notes ox Heating axd Yentilatiox 

principal advantages of indirect steam over hot air are; 
each room has a separate source of heat, the system 13 not 
affected by the winds and no dust or obnoxious gases are 
carried to the rooms. 

The air entering the room will always be as pure as the 
air which furnishes the source of supply. The source 
of heat being independent of the position of the boiler, 
it is. possible to place the indirect radiator anywhere in 
the building and long hot air pipes are not necessary. 
This makes the indirect radiator much more efficient and 
more certain in operation than the hot air furnace. The 
efficiency of this system, from the standpoint of coal 
consumption, will be much less than in direct forms of 
heating and about the same, as the hot air furnace, that 
is, from 50 to 60 per cent of the heat of the coal will 
be used effectively in heating. 

The application of hot water indirect is similar to 
that of steam and the efficiency is practically the same. 

The use of hot water indirects has 

Indirect Hot Wat- been much more limited than the 
er Heating. use of steam indirects. The instal- 
lation of hot water indirects must 
be done with great care so that each radiator will at all 
times have the proper amount of hot water circulating 
through it. In the hot water indirect radiators, if for 
any reason the water in the radiator becomes cooled, the 
radiator will be in danger of freezing. In mild climates 
this difficulty would not be as serious as in locations 
where the weather is extremely cold. 

In buildings of a public or semi-public character where 
a large number of people are to be assembled in a re- 
latively small space, it is neces- 

Fan System of sary to provide adequate ventila- 
Heating. tion. In the systems that have been 

previously described, it is impossi- 
ble to introduce into the room sufficient quantities of air 
to properly ventilate the rooms. It may be said in gen- 
eral that no system of natural circulation has ever Dro- 



Notes on Heating and Ventilation 33 

duced satisfactory ventilation in a room occupied by a 
large number of people; it is necessary to provide some 
means of mechanically circulating the air. This is done 
in the fan system by means of a pressure blower or a 
disc fan. 

In the fan system the pressure produced by the fan 
makes the circulation so positive that it is not affected 
by winds or by the distance of the room from the fan 
itself. The air is taken from the outside, passed through 
the heating coils and forced into the building by the 
faa. 

There are two general methods of heating and ventilat- 
ing with the fan system. In one system the air is first 
passed through a tempering coil, then taken by 
the fan and delivered through a heating coil. 
Each room has a connection both to the hot 
air and to the tempered air chamber. The 
temperature of the air in the room is 
adjusted by taking the air either from the hot air cham- 
ber or from the tempered air chamber. In the second 
system the rooms themselves are heated by means of 
direct radiation and the fan delivers air to the rooms 
only for the purpose of ventilation. In this case no 
heating coils would be necessary. 

In the first method the economy of the system is low, 
as owing to the large amount of air required for ven- 
tilation, the quantity of air introduced into the room is 
ordinarily greater than is necessary for the purpose of 
heating the room. The economy of this form of fan sys- 
tem depends very largely upon the amount of air neces- 
sary, but in most cases its eflficiency would not exceed 
from 40 to 50 per cent, that is only 40 to 50 per cent of 
tlie heat units in the coal would be effective in heating. 
In the combined fan system, where direct radiation is 
used for heating and the fan system for ventilation, the 
economy of the system is better, probably from 50 to 60 
per cent. 



34 Notes on Heating and Ventilation 

The increase in economy of this system is due to the 
fact that it is necessary to run the fans only when it is 
necessary to ventilate the building. 

In addition to the combination just described, of di- 
rect radiation and fan ventilation, there have been de- 
vised innumerable combinations, com- 
Combination of binations of direct and indirect 
Different Sys- steam, direct and indirect water, 
terns. water and hot air, steam and hot air. 

Probably the combinations which 
have been most used have been combinations of direct 
and indirect steam and the combinations of hot water 
and hot air. 

The economy of any heating system depends upon the 
completeness with which the coal in the furnace is burned 

,^ ^ ^ ^n. and the heat lost by the chimney 

The Economy of the , .. ... .. ^ t« ..: 

Tk--ff -I- G + ^^^ *^^ ventilating flues. If, with 

oitterent Systems. ^^^^ ^^ ^^^ ^^^^^ systems the coal 

vras completely burned and all the heat given off were 
used, then each one of the systems would have perfect 
efficiency. 

The losses from any system, given in detail, are as fol- 
lows: Loss through imperfect combustion of coal, through 
the escape of hot gases up the chimney and the loss of 
heat in the air passing up the ventilating flue. 

If the furnace is properly constructed and insures good 
combustion, the loss due to imperfect combustion is small. 
The loss of heat passing up the chimney will depend upon 
the temperature at which the gases leave the chimney and 
the amount of air used to burn a pound of coal. The 
loss by the ventilating flue will depend upon the amount 
of air it is necessary to supply to the rooms for ven- 
tilation. 

If in each of the above systems the hot gases leave 
the heating apparatus at the same temperature, the effi- 
ciency of each will be the same. If the hot gases leave 
the heating apparatus at the same temperature and the 
same amount of air is used for ventilation then the effi- 
ciency of each system will be practically the same. If the 



Notes ox Heating and Ventilation 35 

rooms are not ventilated, then of course, the loss due to 
the heat passing up the ventilating flues will be saved and 
the system will b© more economical. In fact, strictly 
speaking, the loss by ventilation should not be considered 
as entering into the efficiency of the system. This loss 
is entirely independent of the system used and depends 
entirely upon the amount of air which must be supplied for 
purpose of ventilation. It is quite obvious that any 
system involving ventilation will require a greater amount 
of coal. The loss due to ventilation is due to the fact 
that all the heat which is given to the air between the 
temperature of the air outside the building and the air in 
the room is ineffective in heating and is lost up the ven- 
tilating flues. It would be poor policy, however, for the 
designers of heating systems to cut down the amount of 
ventilation in a room in order to save coal. In several 
States there are general State laws which require that a 
certain amount of air to be furnished each person per hour 
in school buildings and other buildings of a public char- 
acter. The necessity and importance of ventilation will 
be discussed under another head. 



Memoranda 



C H A P T E R III. 

THE DESIGN OF A DIRECT STEAM-HEATINQ 

SYSTEM. 

Steam heating is usually done by direct or by indirect 
radiation or by combination of both direct and indirect 
radiation. In small residences occupied by only three or 
four persons it is customary to use only direct radiation. 
The practice, however, is a questionable oec and it seems 
desirable, even in small residences, that some indirect radi- 
ation be used so as to provide a means of ventilation. 
Oftentimes only one indirect radiator is used, bringing its 
air either into the room most used or into the main hall 
so that it may be distributed throughout the house. In 
factories and office buildings where a large amount of air 
is introduced by the opening and closing of doors, it is 
customary to use only direct radiation and in such build- 
ings this is permissible. 

In order to understand thoroughly the operation of a 
steam-heating system one should study the nature and 
properties of steam. Steam is a Nature and Proper- 
watery vapor, and as used in ordi- ^ies of Steam, 
aary radiator practice, always con- 
tains a certain amount of water in suspension, as does 
the atmosphere in foggy weather. 

When water is heated in a steam boiler the tempera- 
ture is slowly increased from the initial temperature of the 
water to the temperature of the boiling point. When the 
water reaches the boiling point small particles of the 
water are changed from water to steam, rise through the 
mass of water and escape to the surface; the water is 
then said to boil. The temperature at which the water 
boils depends entirely upon the pressure in the boiler and 
obviously, as the boiling point increases more and more 
heat is required to produce steam. 



38 Notes on Heating and Ventilation 

Take, for instance^ a given case. Suppose we start with 
water in the boiler at 40 degrees; the pressure in the 
boiler at atmospheric pressure, that is, 14.7 pounds. Un- 
der this condition it will be necessary, in order to increase 
the temperature of the water in the boiler to 212 degrees, 
at which point water will commence to boil, to add 212 — 
40=172 B. T. U's for every pound of water in the boiler. 
In order to convert all the water into steam it will be 
necessary to supply 965.7 heat units, in addition to the 
172 heat units consumed in raising the water to the boil- 
ing point. During the operation of boiling, however, the 
temperature of the water remains constant and the 965 
heat units added in order to change the water at the tem- 
perature of the boiling point into steam are consumed in 
separating the molecules of water and changing the water 
from a liquid into a gas. .This last quantity is termed 
the latent heat and it is the latent heat of water which 
is used primarily in furnishing heat to the room in 
steam heating. As the pressure in the boiler increases the 
latent heat diminishes. The relation of these various 
quantities has been very carefully determined by Regneult 
and compiled in the form of steam tables. The following 
is an abbreviated steam table. More complete tables will 
be found in Peabody^s Steam Tables, or in any of the 
mechanical engineering handbooks. 

STEAM TABLES. 

Column 1 of the Steam Table gives the pressure of the 
steam above the atmosphere in pounds per square inch 
and below the atmosphere in inches of mercury. Column 
2 gives the corresponding temperature of the steam. Col- 
umn 3 gives the heat of the liquid or the heat necessary to 
raise one pound of water from 32 degrees to the boiling 
point, corresponding to the pressure. Column 4 gives the 
latent heat necessary to change a pound of water at the 
temperature of the boiling point into steam at the same 
temperature. Column 5 is the sum of columns 3 and 4, 
and represents the amount of heat necessary to raise a 
pound of water from 32 to the boiling point and then 





Table VI — Properties of 


Steam. 




Pressure 


Tempera- 


Heat of 


Latent 


Total 


Volume of 
1 lb. of 


or vacuum 


ture 


the Liquid 


Heat 


Heat 


steam 


Inches 












mercury 












—12 


137 


105 


1019 


1124 


135 


—10 


160 


128 


1003 


1131 


78.3 


— 8 


175 


143 


992 


1135 


55.9 


— 6 


187 


155 


984 


1139 


43.6 


— 4 


197 


165 


977 


1142 


35.8 


— 2 


205 


173 


971 


1144 


30.6 


Pounds 












per sq. in. 















212 


180.9 


965.7 


1146.6 


26.56 


1 


215 


184 


964 


1148 


25 


2 


219 


188 


961 


1149 


23 


3 


222 


191 


959 


1150 


22.3 


4 


224 


193 


957 


1150.5 


21.2 


5 


227 


196 


955 


1151 


20.16 


10 


239 


208 


946 


1154 


16.3 


15 


249 


218.8 


939.3 


1158.1 


13.7 


20 


258.7 


229.3 


932.5 


1161 


11.85 


25 


266.7 


236.2 


927.1 


1163.3 


10.36 


30 


273.9 


243.5 


922 


1165.5 


9.34 


35 


280.5 


250.2 


917.3 


1167.5 


8.45 


40 


286.5 


256.3 


913 


1169.3 


7.73 


45 


292.2 


262.1 


909 


1171.1 


7.11 


50 


297.5 


267.5 


905.2 


1172.7 


6.61 


55 


302.4 


272.6 


901.6 


1174.2 


6.16 


60 


307.1 


277.2 


898.4 


1175.6 


5.77 


65 


311.5 


281.8 


895.1 


1176.9 


5.43 


70 


315.8 


286.1 


892.1 


1178.2 


5.13 


75 


319.8 


290.3 


889.1 


1179.4 


4.86 


80 


323.7 


294.3 


886.3 


1180.6 


4.63 


85 


327.4 


298.1 


883.6 


1181.7 


4.41 


90 


330.9 


301.8 


881 


1182.8 


4.20 


95 


334.4 


305.4 


878.5 


1183.9 


4.02 


100 


337.6 


308.9 


876 


1184.9 


3.86 


110 


343.9 


315.4 


871.4 


1186.8 


3.57 


120 


349.8 


321.5 


867.1 


1188.6 


3.33 


130 


355 


327.3 


863 


1190.3 


3.1 


140 


360 


332.8 


859.1 


1191.9 


2.92 


150 


365.7 


338.0 


855.4 


1193.4 


2.75 



40 Notes on Heating and Ventilation 

chacge it into steam at the temperature of the boiling 
point. The quantities given in this column are called 
total heat. Column 6 gives the volume of one pound of 
steam at the different pressures. 

EXAMPLES IN USE OF STEAM TABLE. 

Example 1. It is required to convert 10 pounds of 
water at 32° into steam at 100 pounds gauge pressure. 

Solution. — We see from colum-n 5 tliat the total heat 
of 1 pound of steam at 100 pounds pressure is 1,184.9 heat 
units. Then to form 10 pounds of steam would require 
10 times this amount, or 11,849 heat units. 

2. How many heat units will be required to form 5 
pounds of steam from feed water at 100° in temperature 
into steam at 10 pounds gauge pressure? 

Solution. — The total heat of steam at 10 pounds pressure 
above 32° is 1,154 heat units. In this case the feed 
water already contains in it above 32°, 100 — 32=r68 heat 
units. The specific heat of water being 1, the heat units 
required to form a pound of steam will be 1,154 — 68= 
1,086 and to form 5 pounds of steam would require 
5X1,086=5,430. 

3. A steam pipe 8 inches in diameter. The pressure of 
steam in the pipe is 10 pounds gauge. The steam pipe is 
to transmit 1,600 pounds of steam per hour. What will 
be the velocity of steam in the pipe? 

Solution. — Fi'om column 6 of the table we see that the 
volume of 1 pound of steam at 10 pounds gauge pressure 
is 16.3 cubic feet. Then 1,600x16.3=26,080 cubic feet, 
the volume of steam passing per hour. This divided by 
3,600 equals 72, the number of cubic feet passing per 
second. An 8-inch pipe has an area of 50 square inches; 
50-M44=.347 square feet; 72-^.347=208 feet per second, 
which represents the velocity of the steam passing 
through the pipe. This velocity is very high. Ordinarily 
the velocity in steam pipes should not exceed 100 feet 
per second, even in very large pipes. 



Notes on Heating and Ventilation 



41 



Loss of Heat From Radiators. 
In designing a direct steam system it will be necessary- 
first to compute the heat losses from the various rooms by 
the rules previously given. After these losses are deter- 
mined it will be necessary to place sufficient radiating 
surface in the room to supply these losses. In order to 
know the amount of surface that should be placed in a 
room it is necessary to know the amount of heat given off 
per square foot by the different forms of radiators. Heat 
losses for the different forms of radiators are given in 
the following table: 



Table VII — Loss from Wrought Iron Pipe and 


Cast Iron Radiators. 






CAST IKON RADIATORS, 


38 INCHES. 




Df Radiator 

f sq. ft. in 
diator. 




0) 

C3 *- 


steam con- 
l per sq. ft. 
r hour. 


s per sq. ft. 
per deg. diff. 
p. between 
and room. 


^ O Co 




If 


No. lbs 

densec! 

pe 


B.T. U' 

per hour 

of tem] 

steam 


1 column. . .48 sq. ft. 


226 


105 


.212 


1.82 


2 column. . .48 sq. ft. 


226 


67 


.265 


1.65 


3 column. . .45.3 sq. ft. 


226 


88 


.204 


1.42 


6 column. . .36 sq.ft. 


225 


71 


.217 


1.35 


WROUHT IRON 


TUBE^ 


38 INCHES. 




2 column. . .48 sq. ft. 


227 


78 


.274 


1.77 


6 column. ..36 sq.ft. 


226 


81 


.178 


1.13 


CAST IRON RADIATORSj 


20 INCHES. 




1 column. . .12 sq. ft. 


221 


89 


.446 


3.27 


2 column. . .42 sq.ft. 


222 


83 


.284 


2. 


3 column. . .48 sq. ft. 


229 


70 


.294 


1.77 


4 column. . .48 sq. ft. 


226 


73 


.202 


1.27 


1" wall coil, 1 pipe high. 


212 


70 


.41 


2.8 


1" wall coil, 4 pipes high. 


228 


65 


.425 


2.48 



Column 5 is the column which shows the relative effec- 
tiveness of thei various types of radiators. It is obtained 



42 Notes on Heating and Ventilation 

in the following manner: Take, for example, the two- 
column cast iron radiators, results of which are given in 
line 2 of the table. A pound of steam at 226°, as we see 
from the steam tables, gives up its latent heat in con- 
densing which amounts to 965 heat units. This radiator 
condensed .265 pounds of steam per square foot of surface 
per hour. Then 965-f .265=:=255.7, the heat units given up 
by the radiator per square foot per actual surface per 
hour. The steam in the radiator was at a temperature of 
226° and the air in the room at a temperature of 76°, the 
difference in temperature being 150°. If we divide 255.7 
by 159 the result is approximately 1.65. This result rep- 
resents the B. T. U.'s transmitted per square foot of 
rated surface per hour per degree difference of tempera- 
ture between the steam inside the radiator and the air in 
the room. This is the quantity which should be used in 
comparing the relative merits of the various forms of 
heating surfaces. 

The results of a series of experiments made at the Uni- 
versity of Michigan extending over a period of a num- 
ber of years, together with the results shown in the fore- 
going table, leads to the following conclusions: 

Radiators with different steam volumes do not give 
essentially different results, except as the volume is so 
small as to restrict the passage of steam. 

Single column radiators usually show larger results 
than those with more than one column. The condensation 
per square foot of radiator per degree difference is tem- 
perature as shown in column 5 of Table YII shows a 
rapid decrease as the number of columns increases. The 
reason for this is quite apparent when we consider the 

position of the radiating surfaces in 

Different Types. a single pipe radiator as compared 

of with the surface in a three-pipe radi- 

Relative Efficiency . ator. Eeferring to Fig. 5, tube B, 

you will note that this tube can radi- 
ate heat in all directions without interference except 
those lines which radiate to columns A and C. Columns 



Notes on Heating and Ventilation 43 

A and C being at the same temperature, no radiant heat 
passes between them, so that all the surface of column 
B which would radiate its heat to columns A and C is 
unaffected. The amount of surface which does this, how- 
ever, is extremely small. 

SuppQse we take point 1 on column B. The heat from 
that point radiates in a straight line in all directions. 
But all the rays of heat between ray 2 and ray 3 strike 
on column A and are lost because column A is the same 
temperature as column B. The number of rays that do 
this are extremely small in a single column radiator. 

If we consider column B in a three-column radiator and 
take point 1 on column B we see that all the rays between 
rays 2 and 3, rays 4 and o, rays 6 and 7, rays 8 and 9, 
rays 10 and 11 are lost and become ineffective for heating 
as columns A, C, D, E, F, are at the same temperature 
and intercept rays passing into the room. 

When the columns in a radiator have been increased 
from 5 to 6 then the inner columns have practically no 
effect in giving off radiant heat and the only heat which 
they give off is given by convection due to the passage 
of air through the radiator. 

In addition to the experiments given in the table a 
series of experiments were made on radiators painted 
different colors and on unpainted radiators. The results 
of these experiments seem to show that the painting of a 
radiator does not materially affect the heat given off by 
the radiator. 

By glancing at Fig. 5 we see that the greater the 
distance between the columns or pipes of a radiator the 
smaller would be the number of rays of radiant heat inter- 
cepted by other columns of the radiator and the larger 
would be the radiating effect; the wider the space betweeai 
the columns of the radiator the more effective does the 
radiator become in giving off heat. 

The writer has had opportunity to make a series of 
tests on radiators of the two-column type, having the 
sections of one radiator spaced at 2% inches and the sec- 



44 



Notes on Heating and Ventilation 



tions of the other radiator at 3% inches. The increase of 
% inch in the length of space added approximately 10 
per cent to the effectiveness of the radiator. 

Eadiators are made in standard heights. The height 
most used is 38 inches. They can be purchased, however, 




O O 



d/np/e C0/1//7?/?. 




boo 



o o 



poo 



Figure 5. 



in varying heights from 15 to 45 inches. The radiators 
of various heights are rated at a certain number of square 
feet per section. For instance, a 38-inch two-column 
radiator is rated at 4 square feet per section. As a rule, 
however, radiators are slightly overrated. A radiator 



Notes on Heating and Ventilation 45 

containing 48 square feet has an actual surface, when 
measured, of about 47 square feet in most two-column 
radiators. In some cases, particularly in radiators having 
a large number of columns, the radiators are very mneh 
overrated. In one instance a radiator rated at 36 square 
feet had an actual surface of only 27 square feet. In 
purchasing a radiator, therefore, it is important to know 
that it has approximately the surface given in the cata- 
logue of the manufacturer, as the radiating power depends 
primarily upon the square feet of surface it contains. 

Comparing lines 2 and 8 of Table VII you will notice 
that the two-column wrought iron radiator transmits about 
10 per cent more heat than the two-column cast iron 
radiator. This is undoubtedly due not so much to the 
difference of material as to the difference in the spacing 
of the columns composing the radiators. "Wrought iron 
pipe wall coil, as shown in the last line of the table, 
condenses almost twice as much steam as the cast iron 
radiator; in other words, it gives off about twice as 
much heat as the radiator. The reason for this is not 
so much the difference in material as the difference of 
location. In the case of the cast iron radiator the air 
at the base becomes heated, rises along the radiator, be- 
coming more and more heated as it comes nearer to the 
top, so that at the top of the radiator there is little dif- 
ference between the temperature of the air surrounding 
the radiator and the temperature of the radiator itself. 
This reduces the transmission of heat near the top of the 
radiator. In the wall coil, the sections being placed in 
a horizontal position, the air remains in contact with the 
coil for a short time only, so that the air surrounding all 
portions of the coil is practically at the same temperature. 
To state this in another way, in the cast iron radiator, 
with the sections placed vertically, the difference in 
temperature between the air outside the radiator and the 
steam inside the radiator is much less than in the wall 
coil, where the pipes are placed horizontally, making the 
wall coil much more effective per square foot of sur- 



46 



Notes ox Heating and Ventilation 



face. Approximately we can say that a wall coil will do 
twice as much per square foot as a cast iron radiator. 
Their extensive use, however, is always more or less ques- 
tionable, owing to their unsightly appearance and the 
difficulty of installation in many places. 

Besides the usual radiator in which a large proportion 
of the heat is given off by radiation and a smaller portion 

by convection, there is what are 
riue Radiators. known as flue radiators. In a flue 
radiator each section has a project- 
ing flange at the outer edge so that there is confijied in 
the radiator itself a series of narrow hot air flues. In 
these radiators only the external surface of the radiator 
acts as radiating surface. The interior surfaces of the 
radiator act as indirect radiators to heat the air which 
is drawn up from below the radiator. The heat losses from 
two well-known forms of flue radiators are given in 
Table VIII, which gives the loss by radiation from 
the radiator as separated from the loss due to the heat 
transmitted to the air in the flues. 



1 
2 

3 
4 
5 
6 
7 

8 

9 
10 
11 

12 

13 

14 



Table VIII — Heat Loss from Flue Radiators. 

a b 

, Size of radiator 6 sec. 38" 6 sec. 38' 

, Rated surface, square feet 42 42 

. Actual surface, square feet 39 39.41 

. Temperature steam 226 226.9 

. Temperature external air 103.3 103.5 

. Difference between steam and air.. 123 123.4 
. Condensation per sq. ft. rated sur- 
face 1847 .1922 

. B. T. U.'s per deg. diff. per sq. ft. 

rated surface 1.437 1.499 

. Temperature of air entering flues. 106 102 

. Temperature of air leaving flues. .187 182 

. Cubic feet of air leaving flues per 

minute 37.59 45.77 

. Average velocity of air leaving, ft. 

per minute 150.3 171.3 

. Percentage of heat transmitted by 

flues 36 41 

. Percentage of heat radiated 64 59 



Notes on Heating and Ventilation 47 

The action of the flue radiator depends upon the design 
of the flues. There should be no point of restricted flue 
area; that is, the air should be given a free passage from 
the iDase of the radiator to the top. Flue radiators are 
particularly serviceable in rapidly circulating the air in 
the room and can be used in a large room having small 
window surfaces to assist in heating the air in the room 
more rapidly than is done by the ordinary radiator. The 
flue radiator is also used in connection with ventilation, 
in which case the base of the radiator is closed and is 
conuected with the outside air. This phase will be taken 
up more in detail under the head of Ventilation. 

In the foregoing tables it has been assumed that the 
keat lost per degree of difference of temperature between 
the steam in the radiator and the 
air outside the radiator was a con- Heat Lost from 
stant quantity. In general thisRadiators Under Vary- 
may be assumed as true for the ing Temperatures, 
ordinary conditions under which 

radiators operate. Where radiators are operated on very 
high or very low temperatures there is a difference in the 
amount of heat transmitted per degree of difference of 
temperature. Table IX gives the heat transmitted for 
each degree difference of temperature between the steam 
inside and the air outside the radiator per hour per 



Table IX- 


-Heat 


Transmission. 


Difference in 




B. T. 


U.'s transmitted 


temperature. 




per deg. diff. per hr. | 


80 






1.56 


90 






1.57 


100 






1.58 


110 






1.6 


3 20 






1.615 


130 






1.63 


140 






1.645 


150 






1.65 


160 






1.675 


170 






1.69 


180 






1.705 


190 






1.72 



48 



Notes on Heating and Ventilation 



square foot of surface for the two-column cast iron radi- 
ator 38 inches high. 

For ordinary conditions of operation — that is, when the 
steam is at a pressure from atmospheric to 10 pounds 
and the temperature of the room is 70 degrees — there will 
be no necessity to consider this variation in the trans- 
mission of heat due to differences of temperature between 
the steam and the air. There are, however, conditions 
in drying rooms and rooms that are to be kept at a very 




Figure 6. 



high temperature, where this will make an appreciable 
difference in the amount of radiation to be used. In 
vacuum systems also, where a very low vacuum is car- 
ried, it would be necessary to take these factors into 
consideration. 

The following suggestions appfly to the placing of 
radiators in the room. The radiators should te placed 
in the coldest portion of the room. In general it is 



Notes on Heating and Ventilation 49 

best to place the radiators in front 

of the \Tindow, selecting a radiator Installation of Direct 
of such a height that the top will Radiators, 

be an inch or two below the win- 
dow sill. There are a number of 

advantages in placing the radiator in front of the window. 
Probably the most important is the fact that it reduces 
the strong cold down draft along the window surfaces. 

Figure 6 shows the effect upon the circulation of the air 
by placing the radiator in front of the windows. In this 
case we get two separate currents of air. The current 
rising from the radiator divides, one current passing out 
into the room, being cooled by the wall surfaces and ob- 
jects in the room, dropping down to the floor and passing 
back along the floor to the radiator; the other current, pass- 
ing directly to the cold wall surface, is cooled, drops down 
along this surface and comes back to the radiator, mak- 
ing the circulation along the cold walls and windows close 
to the radiator a local one which does not affect the 
occupants of the room. 



Table X — Radiator Tappings. 



For one-pipe work radiators containing — 

Inches.- 

24 sq. ft. and under 1 

From 24 to 40 sq. ft 1^ 

From 40 to 100 sq. ft iy2 

Above 100 sq. ft 2 

For two-pipe work radiators containing — 

48 sq. ft. and under lx% 

From 48 to 96 sq. ft 1^x1 

Above 96 sq. ft iy2xl^ 



Carpets and rugs should not extend under the radiator. 
If a radiator is allowed to stand upon a carpet or rug for 
any great length of time, the heat from the legs of the 
radiator will eventually deteriorate the fabric of the 
rug. In a carpeted room the radiator may be placed 
upon a hardwood or a marble base. 



50 Notes on Heating and Ventilation 

When radiators are placed next the wall a space of 
1% inches at least should be left for the circulation of 
air behind the radiator. 

Unless otherwise specified, radiators are usually tapped 
as in Table X. 

The best method of figuring radiating surface is to de- 
termine the actual heat loss from the room in B. T. U. 's, 
then decide upon the form of radiator which you pro- 
pose to use. Suppose, for example, 
Rules for Direct that a two-column cast iron radi- 
Heating. ator is selected. The steam pressure 

to be carried is 5 pounds. The 
temperature in the room is required to be 70 degrees. Re- 
ferring to the table of heat losses from direct radiators 
(Table IX), we see that a two-column cast iron radi- 
ator loses 1.65 heat units per degree difference of tem- 
perature per square foot of rated surface per hour. The 
temperature corresponding to 5 pounds pressure of steam 
as given in Steam Table (Table VI), is 227 degrees, and 
the difference between this and the temperature of the 
room will be 157 degrees. Then the heat lost will be 
165 X 157 = 259 heat units per square foot per hour. 
Dividing the heat loss, as given by the rule for loss of 
heat, by 259 gives the number of square feet of radi- 
ation to be used. 

This is the only method that can be used at all in 
rooms where conditions are exceptional. For rooms of 
ordinary construction, heated to 70 degrees, a large num- 
ber of thumb rules are used. Some of these thumb rules 
are as follows: 

EuLE 1. Divide the volume of the room by 55, Add 
one-fourth of the exposed wall surface; add the glass sur- 
face, and multiply the sum of these three quantities by 
£75. The product will be the direct radiation in square 
feet, 

EuLE 2. For ordinary rooms. Divide the exterior wall 
surface by 4, add the glass surface and multiply the sum 
"by ,4, 



Notes on Heating and Ventilation 



51 



B, For entrance halls. Divide the exterior wall sur- 
face by 4, add the glass surface and multiply the quo- 
tient by ,54, 

C, For the wall surface in basement rooms below the 
ground line. Divide the wall surface by 4 and multiply 
the result by ,17, 



23-10- - 




52 



Notes on Heating and Ventilation 



D. For floors having unlieated space helow. Divide the 
floor space hy 4 and multiply the result by .23, 

EuLE 3. Divide the volume of the room in cubic feet 
by the factors given below and the quotient luill be the 
radiating surface in square feet. 




Figure 8. 



Notes on Heating and Ventilation 53 

First floor rooms, one side exposed 55 

First floor rooms, two sides exposed 50 

First floor rooms, three sides exposed 45 

Sleeping rooms, second floor 60 to 70 

Halls and hath rooms 50 

Q-fflces 50 to 75 

Factories and stores 75 to 150 

Assembly halls and churches 75 to 150 

EuLE 4. (Baldwin's Eule.) Divide the differences 
between the temperature at which the room is to be Icept 
and that of the coldest outside temperature by the differ- 
ence between the temperature of the steam in the radi- 
ator and that at which you wish to Tceep the room and 
the quotient will be the square feet of radiating surface 
to be allowed for each square foot of equivalent glass sur- 
face. By equivalent glass surface is meant the wall sur- 
face divided by 4 plus the glass surface. 

In all of these rules the factors to be allowed for 
exposure should be applied. These factors are given under 
the head of ^'Factors for Exposure.'' Where the rule 
does not involve the contents of the room it will be neces- 
sary in very large rooms or in rooms where the wall sur- 
face is very small in proportion to the contents of the 
room, to add a certain proportion of radiation, usually not 
more than 10 per cent, to allow for heating the air in the 
room quickly when it has once been allowed to cool. 

In order to understand better the methods of deter- 
mining the heating surface required for a given house, it 
would be best to consider a concrete example. Figs. 7, 

8 and 9 represent the basement, 

first and second floors of a resi- Example. (Direct 

dence. The house is constructed Radiation.) 

of wood, sheathed, papered and 

clapboarded on the outside and 

plastered on the inside. On the first floor the rooms are 

9 feet 6 inches high and on the second floor 8 feet 6 
inches high. The windows are 6 feet high and the stand- 
ard size is 3 feet wide. Table XI gives the general 



54 



Notes on Heating and Ventilation 



dimensions of the room and the heat losses from the 
various rooms, assuming the temperature of the outside 
air to be zero and the temperature of the inside to be 70 
degrees. 



Parlor 13'9"xl2'9"x9'6" 

Sitting room 14'3"xl5'6"x9'6" 

Dining room 12'6"xl3'9"x9'6" 

Kitchen 13'0^'xl3'0"x9'6" 

Hall 12'9"xl0'0''x9'6" 

SECOND FLOOE, 

W. Chamber Il'6''xl3'6"x8'6" 

Alcove . 10'0"x 9'6"x8'6" 

So. chamber 12'6"xl4'9"x8'6" 

N. chamber 13' xl3' x8'6" 

Bath 6' X 8' x8'6" 

E. chamber 13' x 8' x8'6" 

Front Hall 14' x 4' x8'6" 

Front Hall 8' x 6' x8'6" 

Back Hall 3'6"xl2' x8'6" 

N. chamber 13'0"xl3'0"x8'6" 

Bath 6'0"x 8'0"x8'6" 

E chamber 13'0"x 8'0"xS'6" 

Front hall 14'0"x 4'0"x8'6" 

Front hall 8'0"x 6'0"x8'6" 

Back hall 3'0"x 6'0"x8'6" 



c3 


c3 




=is. 


a 


«H 


0«M 




3 


^ p 


a =3 


r- 2? o 


o 


d m 


.t; 32 


B^ 


> 


^ 


t^ 




1665 


216 


36 


9450 


2100 


95 


48 


7035 


1640 


145 


36 


7350 


1610 


249 


36 


10300 


1210 


197 


18 


7035 


1320 


172 


48 


10050 


810 


130 


40 


7560 


1560 


172 


24 


7035 


1440 


188 


24 


7455 


410 


50 


18 


3150 


880 


160 


18 


5250 


885 


33 


18 


2730 


360 


118 


18 


5040 


1440 


188 


24 


7455 


410 


50 


18 


3150 


880 


160 


18 


5250 


885 


33 


18 


2730 


360 


118 


18 


5040 



The method used in determining the British thermal 
units lost from the room, given in column 6, is the same 
as those given in the paragraph headed '^Eules for De- 
termining Loss of Heat.'' Take, for example, the parlor. 
The "NTall surface is 216 square feet. Divide this bv 4; 
the result, 54 square feet, is the equivalent glass surface. 
Add the actual glass surface, 36 square feet, Tvhich makes 
a total equivalent glass surface of 90 square feet. Mul- 
tiply this by 1% times the difference between the out- 



Notes on Heating and Ventilation 55 

side and the inside temperature, which gives the heat lost, 
or 90 X 105 = 9,450 B. T. U. lost from the room per 
hour. The remainder of the results shown in column 6 
have been computed in the same way. 




Figure 9. 

In Table XII the second column gives the B. T. U. 's as 
determined in Table XI; the third column the B. T. U.'s 
corrected for exposure, 10 per cent being added to rooms 
having north and west exposures, as, in this case, the pre- 



56 



Notes on Heating and Ventilation 



vailing winds are from the west. Column 4 gives the 
radiating surface required to heat the rooms with a two- 
column cast iron radiator. Column 5 gives the radiating 
surface as determined by Eule 3. 



Table XII — Results of Computation, Direct System 








rface. 
n 

q. ft. 








c u 


p a ^ 


CO 




M 


:^i 


.5c 

bflo o 


ttln,2i 




. T. TI 
from 
iblo XI 


T. IT.' 

rooted 
exposii 


adiatin 
Two c 
oast ir 


adiatin 
snrfac 
by Ilu 


FiEST Floor. 


M H 


_i^ 


« 


1^ 


Parlor 


9450 


10395 


40 


33.5 


Sitting room .... 


7035 


7035 


27 


38 


Dining room . . . 


7350 


8085 


31 


30 


Kitchen 


10300 


10300 


40 


32 


Hall 


7035 


7770 


30 


24 


Second Floor. 




W. chamber .... 


10050 


11055 


43 


22 


Alcove 


7560 


8316 
7035 


32 
27 


13 
26 


S. chamber 


7035 


N. chamber 


7455 


8190 


31 


24 


Bath 


3150 


3465 


13 


7 


E. chamber 


5250 


5250 


20 


14.7 


Front hall 


2730 


3003 


12 


14.7 


Back hall 


5040 


5040 


19 


6 



The quantities in column 4 are obtained in the following 
manner. The steam pressure to be carried in the radiator 
is 5 pounds. The corresponding temperature of steam 
is 227 degrees. The temperature of the room is 70 de- 
grees. The difference in temperature between the room 
and the steam will be 157 degrees. In the last column 
of Table VII the heat lost for a two-colum.n cast iron radi- 
ator is given as .165 B. T. U. ^s per degree difference per 
hour. Then the total heat lost per square foot per hour 
will be 157 X .165 — 258 B. T. U.'s, that is, each square 
foot of radiator surface will give to the room 258 heat 
units per hour. Dividing the heat lost from the room, 



Notes on Heating and Ventilation 57 

as given in column 3, by 258 will give the results shown 
in column 4. 

In column 5 the radiating surface has been determined 
by Eule 3, which is sometimes called the Volume Eule; 
that is, the cubic contents of the rooms are divided by a 
certain factor, depending upon the location of the room. 
A careful comparison of columns 4 and 5, together with an 
inspection of the plans, will show the inconsistency of the 
volume rule. The volume rule can be used only where the 
room has an average amount of cubic contents, as com- 
pared with its wall surface. To get the best results 
it is better to employ the method that has been used in 
determining the results in column 4. 



58 



Memoranda 



CHAPTEE IV. 

DESIGN OF INDIRECT STEAM HEATING SYSTEM. 

It is seldom that indirect radiators only are installed. 
This is due chiefly to the increased cost of installation and 
operation of such a plant, as compared with a plant using 
both direct and indirect radiation. In a residence heated 
by indirect radiation alone, it will be necessary to in- 
troduce an excess of air over that required by ventilation. 
This materially increases the cost of operation. In design- 
ing an indirect heating plant the loss of heat from the 
building is figured in the same way as with the direct 
system. In using indirect radiation alone it will be 
necessary to introduce enough air so that the heat left 
in the room will supply the loss from the walls and win- 
dows. In order to determine the amount of surface to be 
placed in the room, it is necessary to know the temper- 
ature to which the radiator will heat the air and the 
amount of heat given off by the indirect radiator under 
different conditions of operation. 

The amount of heat that may be obtained from a given 
indirect radiator will depend upon the temperature at 
which the air is taken in, the temperature of the radiator, 
and the cubic feet of air passing 

through the radiator. The follow- jjeat Lost from In- 
ing table gives the relation between direct Steam 

the above quantities, assuming the Radiators. 

temperature of the air entering the 

radiator to be zero, the temperature of steam in the radi- 
ator 227 degrees, the temperature corresponding to 5 
pounds gauge pressure: 

In school buildings and in buildings where the flues are 
of ample size the amount of air passing per square foot of 
radiating surface may be assumed to be 200 cubic feet 
per hour. In residences and buildings where the flues are 



60 



Notes on Heating and \^entilation 



usually small, the amount of air passing per square foot of 
surface per hour does not exceed 150 cubic feet per hour. 
From the results of the tests on indirect radiators given 
above, the following points may be noted: 



Table XIII— Heat Losses from Indirect Radiators 



tCi . 


«M^ 


m 02 


1 =.. t-<H • . 


B • 

CO o 

a? 


O be 

P 


's transmitted pe 

of radiation pe 

diff. in temp, o 

ssing through ra 

and the steam. . 


O . 


a .2 




'^ . 


"^ r, 1— 




02 *» ^ 


; fiJ 


4 r-; +j' OJ 5 Lj 




O -M -t- 
t— ( 


B. T. 

sq. 
degr 
air 
diat 



Stan- 
dard Long 
pin. pin. 



Stan- 
dard Long 
pin. pin. 



Stan- 
dard Long 
pin. pin. 



50 147 140 .125 .15 .80 .95 

75 143 137 .17 .21 1.17 1.27 

100 140 135 .24 .26 1.51 1.60 

125 138 132 .295 .31 1.85 1.90 

150 135 129 .355 .36 2.22 2.20 

175 132 126 .41 .405 2.57 2.47 

200 130 123 .47 .45 2.90 2.72 

225 127 120 .53 .49 3.25 3.00 

250 123 118 .585 .53 3.60 3.20 

275 121 115 .645 .57 3.90 3.40 

300 119 112 .700 .61 4.22 3.60 



If the temperature of the air entering the radiator is 
constant, then the temperature of the air leaving the 
radiator vrill decrease as the amount of air passing through 
the radiator is increased. 

In order to determine the amount of heat transmitted by 
the radiator it is necessary to assume the number of cubic 
feet of air that will pass through the radiator per square 
foot of radiation. You will also note the difference be- 



Notes on Heating and Ventilation 



61 



tween the standard or short pin, and the long pin radi- 
ator. As shown in Table XlII, the temperature at which 
the air is heated by the long pin is less than the tem- 
perature to which the air is heated by the short pin with 
the same quantity of air passing. This is undoubtedly 
due to the fact that the pins are so long that the ends 
become cooled. On the other hand, the long pin type is 



Table 


XIV — Indirect Radiators— Temperature of 






Leaving Air. 




u : 




>• ^;}-? ^ 




>'^i^'^ 




1 • 




(D-d W 




gxi^g 




d • 








































^^^^ 




o.S"^ 












a, g o « 




22 




s « >>. 




5«D t» 




cs5 




d'^^.b 


«35-.^ • 


u-*^ 




^■^ w c3 


s^-^ u S 


0) 




<D o « 


O) O 0) 


QtbD 




afc/3-rl W 


QbC-S S 


BB 
fli 




1-2 >o^ 




H 




H 


H 




standard Long 


Standard Long 




pin. 


pin. 


pin. pin. 


. . 


130 


125 
128 


135 128 
139 132 


10 .. 


134 


20 .. 


139 


132 


144 136 


30 . . 


.144 


136 
141 


149 140 
153 144 


40 .. 


148 


50 .. 


153 


144 


158 146 



a very desirable type to use when one wishes to pass 
large quantities of air, as the radiator has ample air 
passage. This is primarily the work for which it is de- 
signed. The short pin gives better results for ordinary 
houses where small quantities of air pass through the 
radiator. 

Indirect radiators are placed in a chamber or box as 
close as possible to the vertical flue leading to the room 



62 



Notes on Heating and Ventilation 




Figure 10. 



Notes on Heating and Ventilation 63 

which they are to heat. The air is admitted to the radi- 
ator by a duct or flue, connected 
with the outside air. This duct jj^g^allation of In- 
should be supplied with a suitable direct Radi- 
damper and, if possible, be so ar- ators. 

ranged as to close automatically 

when the steam pressure is taken off the radiator. The 
cold air is usually admitted directly beneath the radiator 
and the heated air on leaving the room is taken off at 
one side. 

The casing surrounding indirect radiators is usually built 
of galvanized iron or of matched board, lined with tin. 
If of galvanized iron it should be bolted together with 
stove bolts, so that the casing may be easily removed. A 
much better method, but one which is more expensive, is 
to enclose the radiator in a small brick chamber with 
cement floor. This chamber should be large enough so that 
the radiator is accessible for repairs. Sometimes a duct 
is provided in the radiator casing so that cold air may be 
taken around the radiator and mixed with the heated air 
through a suitable damper, controlled from the room which 
is heated. This is a very common arrangement in school 
buildings. Fig. 10 shows a sketch of an arrangement of 
this kind. 

The pipes or ducts leading from an indirect radiator 
should be carried to the room as directly as possible. It 
is better to have a long cold air pipe, a short hot air pipe. 
A horizontal hot air pipe should be avoided. Where the 
air from the indirect radiator is to be used primarily for 
ventilation it is best to place the hot air radiator near the 
ceiling. 

-The indirect radiators are usually suspended in the radi- 
ator chamber on iron pipes supported by rods hanging 
from the ceiling. There should be at least 10 inches clear 
space betTveen the radiator and the bottom and top of the 
casing. The casing of the radiator should fit the radiator 
as closely as possible so that very little air is allowed 
to pass around the radiator without being heated. In- 



64 



Notes on Heating and Ventilation 



direct radiators should be placed at least 2 feet above 
the water line of the boiler, if they are to be operated 
on a natural system of circulation and should be so ar- 
ranged that the condensed water will drain from them 
without trapping. The tappings of these radiators are 
the same as for double pipe, direct steam radiators. The 
following table gives the general proportions for an 
indirect radiator system: 



Table XV- 


-Size of Flues for 


Indirect Radiator. 


Heating 
surface, 
sq. ft. 


Area 

of cold 

air supply, 

sq. in. 


Area 
of hot 
air supply, 
sq. in. 


Size 

of brick 

flue for 

hot air. 


Size 

of 

register. 


20 

30 

40 


30 

45 

60 


40 
60 
80 
100 
120 
160 
200 
240 
280 




4x12 
8x12 
8x12 
12x12 
12x12 
12x16 
12x20 
14x20 
16x20 


8x 8 
8x12 
10x12 
10x15 
12x15 
14x18 
16x20 
16x24 
20x24 


50 

60 


.... 75 
90 


80 

100 

120 

140 


120 

150 

180 

210 



Heating Effect of an 
Indirect Radiator. 



It is usual to assume that the air enters the radiator 
at zero degree of temperature, in which case it will leave 
the radiator at about 130 degrees, the steam pressure in 

the radiator being 5 pounds and the 
velocity through the radiator being 
200 cubic feet per hour per square 
foot of radiator. Under the above 
conditions an ordinary pin radiator 
will give off 470 B. T. U.'s per square foot, or, say ap- 
proximately 450 B. T. U.'s. Under these conditions the 
air entering the room will be at a temperature of 130 
degrees, and if the temperature of the room is 70 de- 
grees this air will be capable of losing into the room 60 
degrees, or in other words, there is 60 degrees of tem- 
perature available in this air for heating purposes. 



Notes on Heating and Ventilation 65 

SOME RULES FOR INDIRECT HEATING. 

EuLE 1. Divide the wall surface hy 4, add the glass sur- 
face, and multiply the sum hy .6. The quotient will he 
the amount of indirect radiation necessary to heat an ordi- 
nary room, 

EuLE 2. Figure the heating surface the same as for 
direct heating. Add dO per cent. 

EuLE 3. Divide the volume of the room hy 40. The 
quotient is the square feet of indirect surface required to 
heat the rooms on the first floor. For second and third 
floor rooms divide hy 50, and in stores and large rooms 
divide hy 60. 

Take the same house that was used in the problem for 
direct heating. In this case all rooms are to be heated 
by indirect radiation. It is in actual practice an unusual 
arrangement, but it is figured out 

in this way as an illustration Example of Indirect 
merely. Heating. 

The heat loss in this house 
will of course be the same in both direct and indirect 
heating and is given in Table XI. Assume that the air 
enters the radiator at zero degrees and leaves at 130 
degrees; that the steam in the radiator is at 5 pounds 
pressure and that 200 cubic feet of air is passed through 
the radiator per square foot of surface. From the results 
determined in paragraph headed *' Heating Effect of the 
Indirect Eadiator^' each square foot of radiation 
gives off approximately 450 B. T. U 's. If the temperature 
of the room is 70 degrees only 60 degrees of the heat 
given to the air is effective in heating the room. 
As the total amount of increase in temperature is 130 
degrees, only approximately 60-130, or 45 per cent, is 
available for heating. As each square foot of indirect 
radiation gives off 450 B. T. U^s, 45 per cent of 450, or 
200 B. T. U^s, will be available for heating the room. 
The heat loss as given in the table for the parlor is 
10,395 B. T. U's. Dividing this by 200 gives 52, the 



66 



Notes on Heating and Ventilation 



number of square feet of radiation required for the 
room. 

Fifty-two square feet of radiation passing 240 cubic 
feet of air per square foot will pass 12,480 cubic feet of 
air per hour; 12,480 is 3.47 cubic feet per second. Allow- 
ing a velocity of 5 feet per second, 
Size of Hot Air Pipe, the area of the hot air pipe is 

3.47, divided by 5 equals .69 square 
feet. This equals 99 square inches, which is the proper 
area of the pipe. The size of the cold air pipe leading 
to the radiator is usually made three-quarters the size 



Table XVI — Results of Computation, 
Indirect System. 



O 






m 



< 



ah 

CD rt 

< 






FiKST Floor — 

Parlor 10,395 

Sitting room. . . . 7,035 
Dining room .... 8,085 

Kitchen 10,300 

Hall, 2d floor... 15,800 

Second Floor — 
W. chamber, 

alcove 19,370 

So. chamber.... 7,035 

N. chamber 8,190 

Bath 3,465 

E. chamber .... 5,250 



50 
35 
40 
50 
73 



93 
35 
40 
17 
24 



100 

70 

80 

100 

145 



180 
70 
80 
40 
50 



75 
53 
60 
75 
110 



135 

50 
60 
30 
35 



12x12 

8x12 

8x12 

12x12 

12x12 



12x20 
8x12 
8x12 
6x 8 
6x 8 



900 

700 

720 

1,000 

1,500 



1,600 
700 
750 
300 
500 



of the hot air pipe. Table XVI gives the results for the 
whole house computed in the same manner as given above. 
In the table the odd figures and decimals have been 
left off. 

In selecting the size of radiator for a room, it is neces- 
sary to select those that vary by 10 square feet, as indi- 



Notes on Heating and Ventilation • 67 

rect radiator sections are not made smaller than 10 square 
feet per section. In a house where the radiators would 
be quite small, it is sometimes necessary to put two or 
three rooms on the same radiator, as it is not customary 
to make indirect stacks smaller than four sections. There 
is always danger, however, in taking the heat for two 
separate rooms off the same radiator, that the heat will 
not distribute equally between the two rooms. When 
separate rooms are heated from the same radiator, care 
should be taken to see that pipes leading to the two 
rooms have about the same length and as nearly as possi- 
ble the same resistance. 

A much more common arrangement of indirect radiators 
is to put in just enough indirect radiation to give the 
proper amount of air for ventilation and supply the addi- 
tional heat for the room with direct radiation. Each 
system is installed as though the two were separate, 
except that they take their steam from the same steam 
mains and return into the same return pipes. In this 
system the direct radiators can be installed on the one- 
pipe system, but the indirect should be installed on the 
two-pipe system as indirect radiation does not work well 
on a one-pipe system. It is not necessary to put indirect 
radiation into all the rooms of a residence. They are put 
into the principal living rooms, the hall and the large 
bedrooms. Where the house is small it may be necessary 
to put indirect radiation only in the sitting room and in 
the hall. An example of this kind will be taken up under 
the head of ventilation. 



68 Memoranda 



CHAPTER V, 

STEAM BOILERS AND STEAM PIPING. 

Boilers are divided into two general classes — fire tube 
or tubular and water tube or tubulous boilers. The com- 
monest form of boiler used for heating purposes in this 
country is what is known as the 
return flue fire tube boiler. These Types. 

boilers are adapted to plants of 

over 50 and under 200 horsepower and where the pressure 
does not exceed 100 pounds. For pressures above 100 
pounds it is customary to use water tube boilers. There 
is one exception, that is the Scotch marine boiler, which 
is a fire tube boiler and which can be made to withstand 
pressures of 200 pounds and over, as in this boiler the 
fire does not come in contact with the outside shell. 

For heating purposes there have been introduced a 
number of special forms of boiler, a great many of these 
forms being built of cast iron. Cast iron boilers are 
not usually operated at pressures exceeding 20 pounds. 

Any of these forms of boilers may be used for heating 
and the selection of the proper form will depend upon the 
conditions in^each particular case. In selecting a boiler 
the following points should be taken into consideration: 
The boiler must be of sufficient strength to withstand 
the maximum pressure to be carried. This does not 
usually exceed 20 pounds. It must have sufficient heat- 
ing surface in proportion to the grate surface to be 
economical. The stack temperature in a low pressure 
boiler should not exceed 450 degrees; in the best plants 
it does not exceed 300 degrees. The boiler must have 
sufficient liberating surface so that the steam formed in 
the water may escape from the surface of the water, 
without carrying a large quantity of water with it. The 
boiler must have large circulating areas so that the water 
may be circulated freely to the heating surfaces and 



70 Notes on Heating and Ventilation 

the steam formed may pass away from the heating sur- 
faces without restriction. The steam that forms on the 
heating surfaces rises in bubbles and is liberated from 
the surface of the water. If the boiler has insufficient 
liberating surfaces or the circulating areas are contracted, 
the steam cannot rise rapidly enough and bubbles of 
steam remain on the heated surfaces. These bubbles 
prevent the water from reaching the heating surfaces, 
and as steam is a poor conductor of heat this results in 
an overheating of these surfaces. This trouble may be 
very serious, especially in the water tube type of boiler, 
and results in the burning out of the tubes. In cast iron 
boilers the lack of proper liberating surfaces and suf- 
ficient steam space often causes excessive priming. The 
question of circulating area and liberating surface is of 
more importance in a low pressure boiler plant than in a 
high pressure plant, as steam at 5 pounds pressure has 
about six times the volume of steam at 100 pounds pres- 
sure; so that to have relatively the same circulating area 
and liberating surface in a low pressure boiler, we should 
have ^ve times as much as in a high pressure boiler. 

In boilers for heating purposes it is desirable that 
they should have sufficient steam space, and a large 
storage of water, particularly if the plant is V> ^^ continu- 
ously operated. In boilers having large water storage it 
is possible to maintain a steam pressure on the boiler all 
night under banked fires. Where boilers are to be 
operated only occasionally, it may be desirable to have a 
small quantity of water, as each time the boiler is 
started it is necessary to heat all the water in the boiler 
before steam is formed. The ordinary fire tube return flue 
boiler, on account of its large water storage, liberal circu- 
lating areas and large liberating surface, is a popular one 
for heating purposes. 

The heating surfaces in a boiler are those surfaces 
which have water on one side and hot gases on the other. 



Notes on Heating and Ventilation 71 

A boiler should be so proportioned as to transmit as much 
of the heat generated by the fuel 

to the water as possible. Experi- Proportion of Boilers, 
ence has determined that for best 

results in boilers of 50 horsepower and over a square foot 
of heating surface should evaporate not more than three 
pounds of water per square foot of heating surface. For 
small houses, where heating boilers of but a few horse- 
powers are used, it is not usual to allow a square 
foot of heating surface to evaporate more than 2 pounds 
of water and when a square foot of heating surface 
evaporates more than the amounts given above, the trans- 
mission of heat through the plate becomes so rapid that 
all the heat is not removed; the result is an excessively- 
high stack temperature and a corresponding loss of heat. 
Surfaces that have steam on one side and. hot gases on 
the other are called superheated surfaces. It is not 
advisable to have superheated surfaces in a boiler. 

The proportion of grate surface to heating surface de- 
pends upon the kind of fuel and the intensity of the 
draft. In small boilers used for heating purposes it is 
usual to allow one square foot of grate surface to every 
20 to 30 square feet of heating surface. For larger 
boilers, that is, 50 horsepower and over, it is usual to 
allow from 30 to 40 square feet of heating surface per 
square foot of grate surface. 

The rate of combustion for anthracite coal will vary 
from 10 to 15 pounds of coal per square foot of grate 
surface per hour with average draft. With bituminous 
coal under similar circumstances, 12 to 15 pounds will 
be burned in the smaller boilers and from 15 to 20 pounds 
is the larger sizes. 

The air opening to be allowed in the grates depends 
upon the kind of coal, but usually does not exceed 50 
per cent of the area of the grate. Anthracite and the 
better grades of bituminous coal do not require as large 
opening as do the slack coals. 

The term boiler horsepower as applied to boilers has 



72 



Notes on Heating and Ventilation 



no definite value and varies with local customs, and the 
opinion of the manufacturer. 

The rating of a boiler should be 
Boiler Horsepower, the amount of steam it can 
evaporate with good economy and 
without producing wet steam. In purchasing a boiler 
specify the number of square feet of heating surface the 
boiler should contain. This is a better criterion of the 
work that the boiler will do than the horsepower rating. 
The American Society of Mechanical Engineers has 
adopted the following rating for the horsepower of a 
boiler: 



Table 


XVII— 


Cast Iron 


Boilers 


for 


Steam : 


Heating. 






£ 




*o 




c c3 


1^ 

<d 






u 




c 


.2 o 


« 


n 


o 


fc^ 


rt f" o 


ce . 


^ • 5 




i 


GO 


9 

CO 

bo . 


O OJ S 




rt-w CO 


B 


.s 






*;^« 


^i3£ 




C8 


(0 


2 




C/3 « Sd 


^"" 


<^" 


A. . 


750 


5.04 


90 


17.8 


149 


.42 


B.. 


700 


4.8 






146 




B.. 


80O 


5.25 






155 




C. 


750 


6.25 


120 


19.2 


120 


6.25 


C. 


. 3,400 


25.00 


540 


21.6 


136 


63. 



A boiler horse power is 34y2 pounds of water evaporated 
from feed water at 212 degrees to steam at 212 degrees, 
which is called the from and at evaporation. According to 
this rule, if three pounds of water are evaporated per square 
foot of heating surface, we would allow from 10 to 12 
square feet of heating surface for each boiler horse power. 

In order to give some idea of the proportions used by 
the various cast iron boiler manufacturers, the following 



Notes on Heating and Ventilation 73 

table has been compiled which embodies the practice of 
three makers of standard cast iron 

heating boilers. The different Proportions of Cast 
makers have been designated by Iron Boiler. 
the letters ''A,'' ''B/' ''C' 

STEAM PIPING. 

In designing a system of steam piping the three follow- 
ing considerations are the most important: First, that 
the piping shall be so arranged that all condensed water 
shall drain from it; second, that it shall be free to expand 
that is, so arranged that the joints shall not be strained 
when the piping is heated; third, that all points in the 
piping at which air would accumulate shall be provided 
with some means of removing the air. 

In this article the different parts of the piping system 
referred to will have the following meaning: 

Mains. — ^Mains are those pipes which lead from the 
boiler or boiler header to the submains or risers. Usually 
there are no radiators tapped from these mains. 

Risers. — Eisers start from the mains in the basement or 
attic, and extend up or down through the building. From 
the risers the connections to the individual radiators are 
taken. 

Returns. — All piping carrying condensed water from 
the steam mains to the boiler is included in the return 
system. The terms return riser, return main, etc., have 
the same significance as in the steam system. 

Reliefs or Drips. — A small pipe connecting the steam 
to the return system so as to carry condensed water to the 
returns is called a relief or drip. Drips are used at all 
points where water would collect in the steam system. 
These drips are sometimes made of large pipe and called 
equalizing pipes, serving to equalize the pressure. between 
steam and return mains in gravity return systems. 

Pitch. — The pitch of a pipe refers to its inclination 
from the horizontal pipe lines. It is best that pipes should 
pitch with the current of the steam, so that the steam 



74 Notes on Heating and V^entilation 

will assist in the removal of the condensation. Return 
pipes are usually pitched toward the boiler so that the 
system may be drained at that point. 

Water Line. — The water line is the height at which the 
water stands in the return pipes. In a well designed 
gravity system it is seldom more than six inches above 
the water line of the boiler. 

Siphon. — When a vertical bend is made in the return 
main so that the return dips down and returns to its 
former level, it is called a siphon. All siphons should be 
provided with a drain (or pet cock). 

Dams. — Sometimies the water level in the boiler is lower 
than that desired in the piping system and an inverted 
siphon is placed in the return pipe. No return will then 
take place until the water Has reached the highest point 
of this bend in the return. A dam should be provided 
with an air cock. 

Water Seal. — Where a return pipe enters the return 
main below the water line it is said to be sealed. It is 
customary to seal all main riser drips and returns from 
indirect radiators and pipe coils. 

Water Hammer. — The rattling and the hammering often 
heard in pipes is called water hammer. It is caused by 
steam coming in contact with water or surface in the 
pipes which is colder than itself. A sudden condensation 
results and a vacuum is produced into which the water 
rushes. The blow is often so severe as to crack the fitting 
and spring the valves. It is most apt to occur when the 
plant is first started. Accidents from this cause may be 
avoided by admitting the steam very slowly at first. 

Steam Traps. — Steam traps are vessels usually placed 
between the steam and the return system to allow the 
water of condensation to be carried to the return sys- 
tem without steam entering the returns. By the use of 
steam traps the steam and return mains may have a 
wide difference of pressure. Steam traps are objection- 
able as they are liable to get out of order and require 
frequent repairs. 



Notes on Heating and Ventilation 



75 



The systems of piping may be grouped under three gen- 
eral heads. First, the one-pipe system. In this system 
the pipe carrying the steam to the radiator also returns 
the condensed water from the radi- 
ator to the boiler. Second, two-pipe Systems of Piping. 
system, in which one set of pipes is 
used to carry the steam to the radiator and an entirely 




Figure 11. 



separate set of pipes is used to carry the return water to 
the boiler. Third, a combination of these two systems. 
The usual arrangement in the combination system is to 
run the mains on a two-pipe system, but the connection 



76 



Notes on Heating and Ventilation 



between the mains and the radiators is on the single pipe 
system. The one-pipe system has certain fundamental 
advantages over the two-pipe system. In the one-pipe 
system the steam and condensed water are always at the 
same temperature and as a result there is very little op- 
portunity for water hammer. In the two-pipe system the 
steam and water being separate the water may become 




Figure 12. 

considerably cooled below the temperature of the steam, 
and if at any point in the system it again comes in con- 
tact with the water we have condensation of the steam, 
vacuum forms, causiug water hammer. In large plants, 



I 



Notes on Heating and Ventilation 



77 



however, the one-pipe system is not desirable as it 
necessitates carrying a very large quantity of water 
in the steam mains. 

One-Pipe System. — The simplest of all piping systems 
used in steam heating is what is known as the one-pipe 
gravity system. In this system, the steam generated in 




Figure 13. 

the boiler flows through the pipes to the radiators where 
it is condensed. The condensed steam in the radiators 
flows back through the same piping system to the boiler. 
This arrangement necessitates the condensed steam flow- 



78 



Notes on Heating and Ventilation 



ing back against the current of the steam. This is ob- 
jectionable as there is a tendency to trap the water. Be- 
cause of this tendency it is good practice to make the 
pipes larger in size than would be the case if the steam 
and water flowed in the same direction. In the one-pipe 
gravity system the pipe should always be given a good 




Figure 14. 

pitch toward the boiler. Figure 11 shows the piping and 
radiator connections for a one-pipe system. 

Two-Pipe System. — In the two-pipe system one sys- 
tem of pipes supplies the steam and another system carries 
off the water of condensation. The principal object in 



Notes on Heating and Ventilation 79 

the two-pipe system is to avoid the accumulation of any 
great amount of water in the radiators or mains and in 
that way give a more positive circulation. Figure 12 
shows the general arrangement used in the two-pipe sys- 
tem. The indirect radiators and pipe coils should always 
be connected on the two-pipe system. 

Combination System. — In ordinary buildings the most 
satisfactory method is to use a com.bination of the one- 
pipe and the two-pipe systems. In this system^, as shown 
in Figure 13, the radiators and risers are on the one-pipe 
system, while the mains are installed on the two-pipe 
system. The system has this advantage over the one- 
pipe system of mains, that the mains are not obliged to 
carry so much water of condensation and can be freed 
from water from time to time. The one-pipe radiator con- 
nections of this system are more desirable than the two- 
pipe radiator connections in that there is but one valve 
to get into trouble instead of two and the steam and the 
water of condensation are always in contact with each 
other — thus avoiding the danger of water hammer. The 
risers may be one-pipe, as it is very seldom that we have 
difficulty with the circulation in using vertical risers. In 
most cases the one-pipe radiator connections and two-pipe 
mains will be found to give the best satisfaction. 

Overhead Distribution. — In office buildings and build- 
ings where the basement space is valuable for rental pur- 
poses, it is desirable to place the steam mains where they 
will occupy the least desirable space. It is customary to 
run a vertical steam main to the attic. A set of dis- 
tributing m^ains is run through the attic, from which ver- 
tical risers extend down through the building with drip 
pipes connecting to the return system at their lower 
ends. The radiators are connected to the risers by means 
of single-pipe radiator connections. This system gives 
very satisfactory results, as in all cases the currents of 
steam and water are in the same direction. In buildings 
exceeding four stories in height it is usually necessary to 
provide some form of flexible connection to allow for 
expansion. A system of this kind is shown in Figure 14. 



80 



Notes on Heating and Ventilation 



Gravity System. — Figures 11-14, inclusive, are all shown 
for gravity return system and this system is the one com- 
monly used for all small buildings and for residences. 
In this system the steam and return mains are connected 
to the boiler without the introduction of pumps or traps, 
so that the condensed steam flows back to the boiler by 
gravity. Figure 15 gives a diagrammatic sketch of such 




Figure 15. 

a system. If the pressure at the surface of the water in 
the boiler is the same as the pressure of the surface of 
the water in the return mains, then the water level in 
the return mains and in the boiler will be the same. 
But if, as shown in Figure 15 by the dotted lines, the 
pressure in the boiler is 5 pounds and the pressure is 
only 4 pounds when it gets to the ends of the system, then 



Notes on Heating and Ventilation 81 

the system is no longer balanced. It is necessary for the 
water to rise in the return mains until the column of 
water in the return mains is equal in height to the 
pressure of 1 pound, or approximately, it must rise about 
2.31 feet so that the water in the return main will be 2.31 
feet higher than the water in the boiler, and this will be 
true for each 1 pound difference in pressure between the 
steam at the boiler and the steam at the extremities of 
the system. It is necessary, then, to be very careful to 
have ample sized piping in this system so that the 
pressure at all points of the return main will be about 
equal. In addition, it is necessary that the steam radi- 
ators, both direct and indirect, be at least 2 feet above 
the water line. For the reasons given above it is not 
desirable to operate large plants on the gravity return 
system, as this system requires larger expense for steam 
mains and more or less difficulty will always be experi- 
enced in starting up the system. The systems of circula- 
tion involving traps and pump circulation will be taken 
up under the head of Central Heating Systems. 

There are a great many rules given for determining the 
size of steam return mains, all of which must be more or 
less modified to meet the particular case in hand. In fact 
a very careful determina- 
tion of the size of main is Size of Steam Return Mains. 
not necessary, as, no matter 

how carefully we calculate the size of the main, it is 
necessary to take the nearest pipe size. In determining 
the size of the main two conditions must be considered. 
First, it must be of suffi,cient capacity to allow of free 
circulation. This is the principal consideration in smaller 
buildings. Second, the mains must not produce more than 
a certain amount of pressure. This point is of particular 
importance in the design of central heating systems. In 
the case of residences, the size is determined by rules 
determined by practice. In the second place, the laws 
governing the amount of pressure in steam pipes are fairly 
well known. They will be treated under the head of 
Central Heating Systems. The most rational method of 



82 Notes on Heating and Ventilation 

finding the size of mains is by determining the velocity 
of steam passing in the main. Knowing the weight of 
steam passing in the main and having the pressure, the 
volume of steam passed by the main is known. This vol- 
ume divided by the allowable velocity in feet gives 
the area of the pipe in square feet. The velocities 
allowed in various forms of mains are as follows: 

In steam engine connections from 75 to 100 feet per 
second. 

In exhaust steam mains from 75 to 150 feet per second. 

For steam heating work on the one-pipe system, 2 
inches and under 10 feet per' second. 

For two-pipe work pipes 2 inches and under 15 feet per 
second. 

For two-pipe work pipes 4 to 2 inches 25 feet per second. 

For two-pipe work pipes 2 and 4 inches 15 feet per 
second. 

For two-pipe work pipes 4 inches and over 30 feet per 
second. 

Example. — Assume that a main is to supply 4,000 feet of 
radiation. This radiation gives off approximately 1.68 
B. T. U's per square foot of radiating surface per degree 
difference of temperature. Let the temperature of the 
steam be 220°, the temperature of the room 70°. Then the 
total B. T. U's transmitted per hour will be 200— 70X1.68 X 
2,000=504,000. At 220° the latent heat of steam taken 
from the steam tables equals 960 B. T. U^s. Then the 
steam used per hour will be 504,000-^960=525 pounds of 
steam. At 220° each pound of steam has a volume of 
22.95 cubic feet. Hence we have 525X22.95=12,048 cubic 
feet per hour or 3.4 cubic feet per second. For a velocity 
of 25 feet per second we must have a pipe with an area 
of 19.23 square inches. This is approximately the area of 
a 5-inch pipe. 

The following is a very common rule for gravity re- 
turn systems: To determine the diameter of the main 



Notes on Heating and Ventilation 83 

leading from the boiler, point off two places in the number 
expressing the radiating sur- 
face and take the square foot Miscellaneous Rules for 
of the remainder. To apply Size of Steam Main, 

the above rule for indirect sur- 
faces, multiply the indirect surface by seven-fifths and 
proceed as for direct surface. As an example, suppose we 
are to supply 2,000 square feet of direct radiation. We 
point off two places, which gives us 20. The square root 
of 20 is 4.48, which would make the size of the main 4% 
inches. 

Table XVIII gives the common practice in pipe sizes: 




50 11/2 inch 1 14 inch 1^4 inch 1 14 inch 

100 2 inch 1 V2 inch 1 1/2 inch 1 V2 inch 

150 2 inch iy2 inch 2 inch 1% inch 

200 2^ inch 2 inch 2 V2 inch 2 inch 

250 21/2 inch 2 inch 2 1^ inch 2 inch 

300 3 inch 2^2 inch 3 inch 2y2 inch 

400 3V2 inch 3 inch 3 inch 2y2 inch 

500 3V2 inch 3 inch 3 inch 3 inch 

600 3y2 inch 3^ inch 

800 4 inch 3y2 inch 

1,000 4y2 inch 4 inch 

1,500 4y2 inch 4 inch 

2,000 5 inch 4 1^ inch 

3,000 6 inch 5 inch 

4,000 7 inch 6 inch 

6,000 8 inch 7 inch 



The steam supply of the radiator should never be less 
than 1 inch. Steam mains in one-pipe work should not be 
less than 1% inches and in two-pipe work less than 1% 
inches. The return connections to radiators should not 



84 



Notes on Heating and Ventilation 



be less than %-inch and return mains should not be less 
than 1 inch. The drip pipe should not be less than 
%-inch. Long horizontal pipes should be one-pipe size 
larger than the verticals in the same line. In the over- 
head system, especially where the building is over seven 
or eight stories, it is well to make the risers fairly large 
at the lower end to take care of the condensed steam. 
These risers, even at the lower end, should not be less 
than 2 inches in size. 

Return Mains. — Eeturn mains cannot be figured for 
returning the water of condensation at a low velocity 
alone, but allowance must be made for the very sudden 
demands which occur when the plant is started and for 
the air carried with the water. The size of return main 
is determined almost entirely by practical considerations. 

Table XIX gives the relative size of steam and return 
main and diameter of steam main. 



Table XIX- 


-Relative 


Size of Mains. 


Diameter 




Diameter 


Steam Pipe. 




Return Pipe. 


iy2 




1 


2 




ly* 


2V^ 




1V2 


3 




iy2 


4 




2 


5 




2y2 


6 




3 


8 




4 


10 




5 


12 




5 or 6 



Return mains may be placed on a dead level, but as a 
rule it is desirable to give them some slight pitch, to 
some point, preferably the boiler. At its lowest point 
there will be provided some sort of drain cock so that all 
condensed steam may be drained out of the system. 

This is one of the most important things to be consid- 
ered in any well constructed system of piping. The radi- 



Notes on Heating and Ventilation 85 

ators, as well as the pipes, should be set so that the 
condensed steam may drain from them 
easily. It is always best to drain the Pipe Drainage, 
condensed steam with the steam, in 
which, case the steam tends to free the pipes of the water 
of condensation. If mains are long, it is well to drain 
them at intervals to avoid carrying too much water of 
condensation with the steam. In the gravity return sys- 
tem where the drip pipes connect to the return system, 
there should be at least two feet difference in level be- 
tween the steam main and the boiler water level, in 
order to avoid the possibility of the water from the boiler 
being forced back into the steam main. Check valves 
will not prevent it, the water of condensation will accu- 
mulate in the steam main above the check. If it is neces- 
sary to drip the steam main at a point below or close to 
the water line, then it should be drained to a separate 
system of piping and the condensed steam accumulating 
in this piping should be forced back to the boiler by some 
mechanical means. Steam connections to steam mains 
should always be taken from the top of the mains so as 
to avoid the draining of the water of condensation into 
the connections. In overhead systems of piping the steam 
mains may be drained directly through the risers as the 
amount of condensation is small compared to the number 
of drain pipes. In this case the risers may be taken from 
the bottom of the main. In connecting radiators to the 
pipe system they should be set so as to have a slight 
pitch in the direction in which they are intended to drain. 
Eadiators set so that they cannot be entirely drained are 
a very common source of water hammer. 

The expansion of pipes in mains exceeding 50 feet in 
length becomes an important consideration. It is cus- 
tomary to assume that in low-pressure steam piping there 
will be an expansion of 1% inches 

per 100 feet of pipe. In steam Expansion of Pipes, 
mains carrying a pressure of 80 
pounds or over it is customary to allow for an expansion 



86 



Notes on Heating and Ventilation 



I 



of about 2 inches per 100 feet of length. There are three 
general methods of taking up expansion. 

First, a simple means is by making offsets and turns in 
the pipe every 50 to 100 feet, the expansion being taken 
up by the spring in the pipe. This is snown in Fig. 16. 
This method is seldom used except in pipes under 4 
inches. Another method and the method which it is most 
desirable to use is to take up the expansion at all 90° 
turns. In this method the pipe when it reaches the cor- 
ner turns either up or down and the expansion is taken 
up by the movement around the vertical nipple in the 



HH. 



Figure 16. 

elbows or tees at the corner. This method of taking up 
expansion is shown in Fig. 17. The author has had the 
opportunity of observing a system installed, in which ex- 
pansion amounting to as high as 4 or 5 inches has been 
taken up in swing joints and the joints (which have been 
in use for over seven years) have given no trouble what- 
ever. 

The third method is by use of expansion joints. The 
use of expansion joints is in general not to be recom- 
mended. Fig. 18 shows a cross-section of an expansion 
joint. Expansion joints are quite expensive and are 
always liable to leak and require attention. By carefully 
laying out the piping most systems can b'3 installed with- 
out the use of expansion joints. The most serious diffi- 
culty occurs in the modern high office building. In build- 



Notes on Heating and Ventilation 87 

ings of not over ten stories expansion joints may be 
avoided by anchoring the risers in the middle so that they 
expand in both directions, and allowing for a flexible 
connection between the risers and supply main in the at- 
tic and return main in the basement. In this case the 
radiators in the upper and lower stories of the building 
must have allowance made in the radiator connections foi 
expansion of the main. 




Figure 17. 

Another method that has been used to allow for expan. 
sion is by offsetting the pipe at about the middle story. 
As, for example, in a building of say 16 stories, run the 
riser up to the eighth story, then offset just under the 
ceiling of the eighth story for a considerable distance, 
usually not less than 20 feet, and continuing the riser up 
at another location. The principal objection to this 
method is its appearance. In some cases it is difficult 
to avoid the use of expansion joints. In using expansion 
joints, the joint should be anchored so that the expansion 
will go in a definite direction. 

A great deal of consideration should be given to the 
valving of a steam heating system. Gate valves should 
be used on horizontal steam mains, as they do not form a 
water pocket. If globe valves are used on 
steam mains, they should be placed horizontally 



88 



Notes on Heating and Ventilation 



to avoid forming a steam pocket. Where it is 

possible to use it, an angle valve makes a very desirable 
form of valve. In large buildings where the plant will 
be under the control of a janitor or engineer, it is desir- 
able to place valves on the steam risers and valves on the 
corresponding return risers. In residences it is well to 
avoid valves, particularly on return mains. A valve on 
the return main is particularly dangerous as it may be 
closed by accident while the system is in operation, in 
which case, the radiator will be filled with water and no 
water will be allowed to return to the boiler. 




Figure 18. 

Location of Mains and Risers.— Mains and risers should 
be located in as inconspicuous a place as possible, at the 
same time they should be accessible. The concealing of 
mains and risers in the building construction is always a 
questionable practice. If it is necessary to conceal the 
pipe it should be concealed under panels screwed on so 
that they can be removed in case of leakage or other 
necessary repairs. It is not wise to attempt to save in 
risers by making long radiator connections. The system 
will give much better operation by having frequent risers 
with shorter radiator connections. Where risers are con- 
cealed in a building of wooden construction they should 
be carefully protected from the woodwork. 

Protecting Pipes. — Where steam piping comes through 
floors and walls it should be protected by a sleeve and be 
provided with floor and ceiling plates. This sleeve is 



Notes on Heating and Ventilation 



89 



usually made of galvanized iron in two pieces so that it 
can be telescoped to fit any desired thickness of floor. 

The connection between the radiators and the risers 
should always be carefully considered and where the radi- 



/t\ /T\ /h /t\ /r\ /1\ A A /t\ 




Figure 19. 



ator is very close to the steam main it is necessary to 
consider the expansion of the 

riser. Fig. 19 and Fig. 20 show Radiator Connections. 
different methods of connecting 

radiators so as to allow for expansion. Tn wooden build- 
ings the radiator connections are very often concealed in 
the floor. Where this is done it is best to enclose the 
piping in galvanized iron case and the flooring over the 
pipe should be laid so that it can be removed. In build- 
ings of fireproof construction, it is not possible to enclose 
the piping in the floor, and it is usually necessary to run 



90 



Notes on Heating and Ventilation 



the piping above the floor, as in Fig. 20. The commonest 
method of connection where expansion is to be allowed 
for is to run the radiator connection behiad the radiator 
and connect the radiator at the side opposite the riser. 

Supporting of Pipes. — Horizontal pipes are usually sup- 
ported by the ordinary form of expansion hanger. As a 
rule pipes should be supported every 10 feet and should 
be supported at points bearing the greatest weight. In 
placing a pipe support care should be taken to see that 
each support bears its proper proportion of weight. In 
buildings over three stories in height other methods 




Figure 20. 



should be taken to take the weight of the risers. An 
iron strap passing around the pipe and bolted to some 
portion of ,the building structure is usually the best 
means. Large piping is often supported by chains or on 
brackets with rollers. The supports of large pipes will 
be taken up under the subject of Central Heating. 

In the larger buildings the connection between the 
risers and the mains should be such as to allow for the 
expansion of both riser and main, and in the smaller 
buildings for expansion of the main. Fig. 21 shows 
two forms of connections used — the horizontal pipe should 
not, as a rule, be over 10 feet long and should be given 
a sharp pitch toward the main. It is always prefer- 
able to take the steam connection from the top of the 
main so that none of the water of condensation will be 
carried into the riser. 



CHAPTER VI. 



VENTILATION. 

The necessity of ventilation, that is, of renewing the 
air in a closed room, is due, first to the vitiation of the 
air by the products of respi- 
ration from the persons in Necessity of Ventilation, 
the room; second, to the 

products of combustion from artificial illumination; third, 
to the hea.t generated by persons and lights in the room; 
and, fourth, to the presence of gases from chemical pro- 
cesses. 

In a small house or a small school building ventilation 
Is very easily produced by methods which employ natural 
draft, such as hot air furnaces, steam and indirect radi- 
ators. In all systems using natural draft, the force of 
the draft depends upon the difference of the temperature 
between the air inside and that outside the flue. Where 
this difference amounts to only 30° or 40° the difference 
in the weights of the columns of air is so small that the 
force producing draft is very light and may be easily 
overcome by external conditions. In larger buildings it 
is not possible to use natural draft as the flues become 
excessive in size and are not certain enough in their oper- 
ation. This has led to the use in school buildings and 
other public buildings of a forced system of ventilation 
in which the circulation is produced by a fan or system 
of fans. 

The perfectness of the ventilation in a room is ordi- 
narily determined by the amount of carbonic acid gas. 
Carbonic acid gas is not poisonous in itself. Its injurious /^ 
effects are produced entirely by the reduction of the • 
oxygen in the room. There are, however, other injurious 
gases given off from the body, together with the carbonic 
acid gas. 



92 Notes on Heating and A^entilation 

Products of Respiration. — The lungs take in oxygen 
from the air which combines with the tissues of the body 
forming the products of combustion which are given off 
by the excretory organs — lungS; kidneys, skin, etc. The 
principal excretions removed by the lungs are carbonic 
acid gas, water vapor mixed with other gases and some 
animal matter. These excretions, together with excre- 
tions from the skin, produce a disagreeable odor and 
may be poisonous. The average man when sitting still 
consumes in breathing from 19 to 25 cubic feet of air per 
hour and when exercising from 26 to 35 cubic feet per 
hour. The amount of carbonic dioxide and water vapor 
given off by human beings is given in the following table: 



Table XX— Air Pollution Tests. 


Subject of Test 




At Work 






At Rest 


6S^ 


1- 


6^. 


CO 

O.S 


Sbi, 




O . 


CO 

O.S 

« C3 




5^ 


-^5 


ffio 




5^ 


^S 


X^ 


Laborer . .45 


SI 


1.515 


2.03 


69 


20 


.551 


1.12 


Laborer . .77 


47 


1.423 


8.05 


78 


26 


.586 


2.55 


Clerk 64 


44 


1.331 


1.768 


69 


29 


1.141 


11.966 


Draughts- 
















man . . .69 


41 


1.61 


1.61 


, , 


, . 


.... 





Average 
















man 


. . 


.... 


.... 


66 


63 


.412 


1,365 


Woman .... 


. 


.600 


.... 


. 


. 


.... 




Bov 




.48 


.... 










Girl 




.39 


.... 






.... 





Products of Combustion. — The products of combustion 
from the sources of heating, such as grates, stoves, etc., 
are drawn off* by the chimney, but the products of com- 
bustion from the lights in a room pass directly into the 
room. Lights give off carbonic acid gas, watery vapor, 
and traces of sulphuric acid. Table XXI gives the con- 
sumption of combustibles and the generation of carbonic 



Notes on Heating and Ventilation 



93 



acid gas by ordinary forms of lighting. The table is given 
for each normal candle power: 



Table XXI — Pollution by Lighting. 

Consumption of com- Carbonic acid 

bustible per C. P. per C. P. in 

Source. in cu. ft. per hr. cu. ft. per hr. 

Gas — Fishtail burner 802 — .527 .494 — .304 

Gas — Argand burner — .445 .254 

Gas — Welsbach burner . . . .053 — .024 .030 — .057 

Petroleum, round burner .. Gals. .00050 .112 

Petroleum, small flat bnr. .Gals. .00198 .335 

Wax candles Oz. .271 .417 

Paraffine candle Oz. .324 .459 



The products of chemical operations should never ac- 
cumulate in a room so that the odor is perceptible. In 

some industrial processes it is al- 
chemical Processes, most impossible to avoid a certain 

amount of concentration of the 
gases. In such a case the chemical products should be 
sufficiently diluted with fresh air so as not to produce 
injurious effects upon the occupants of the room. 



■ £1 





Figure 21. 



Table XXII gives the relative dilution required for dif- 
ferent gases in cubic feet per 100 cubic feet of air: 



94 Notes on Heating and Ventilation 



Table XXII — ^Air Dilution. 



Detrimental effect occurs 
in several hrs. in i^-l hr. 



Iodine vapors 00005 .0003 

Chlorine or bromide vapors 0001 .0004 

Muriatic acid 001 .005 

Sulphuric acid .005 

Sulphureted hydrogen .02 

Ammonia 01 .03 

Carbonic oxide 02 .05 

Carbonic acid 1.00 8.00 

Carbureted hydrogen 6.56 gr. 



Generation of Heat by Human Beings. — The amount of 
heat generated by a human being varies with age, activ- 
ity and temperature of the surrounding air. The average 
amount of heat given off by an adult is about 400 B. T. 
U's per hour and by a child about half that amount, or 
200 B. T. U's per hour. Of 445 B. T. U's given off by 
human beings about 30% is lost by contact of air and 
about 43% by radiation, the balance is lost by exhalation 
and other losses. Comparing this with the average steam 
radiator, we see that a child is equal to about eight- 



Table XXIII — Heat Given Off by Illuminants. 

Total B. T. U.'s Heat radiated, 

Source. given off. B. T. U's. 

Gas — Fishtail burner 313 32 

Gas — Argand burner 198 28 

Gas — Welsbach burner 32 6 

Petroleum 158 42 

Incandescent lamp 14 10 

Arc lamp 2.5 



tenths of a square foot of radiation and an adult man is 
equal to about one and eight-tenths of a square foot of 
radiation. This becomes a very important point in the 
heating of large halls, particularly if they are very 
crowded and have very little external wall space, as the 



Notes on Heating and Ventilation 95 

heat given off by the persons in the room may be more 
than sufficient to warm the room, which will necessitate 
providing for the removal of this heat from the room. 

Generation of Heat by Illumination. — The foregoing 
table gives the heat generated by different sources of 
illumination per candle power per hour. 

Ordinarily the heat given off by electric lights is so 
small as to be incalculable, but where oil lamps, candles, 
or gas lights are used, the heat given off is appreciable, 
except in the case of the Welsbach burner, which gives 
off relatively a small amount of heat. The ordinary fish- 
tail burner is equal to about one and four-tenths square 
feet of radiation. 

Changes of Air Necessary. — In order that the air in a 
room occupied by human beings may be reasonably pure 
it should be diluted with fresh air. The amount of the 
dilution, except where chemical processes are to be con- 
sidered, is usually determined by the per cent of carbon 
dioxide present which is assumed to be proportional to 
the products of respiration. The carbon dioxide itself is 
not injurious, but it serves as an indication of the pres- 
ence of other injurious substances. It is usually assumed 
that carbon dioxide is uniformly distributed throughout 
the room. This, however, is not strictly true, as carbon 
dioxide is a very heavy gas and naturally accumulates 
at the floor. x\ir that contains more than ten parts of 
carbon dioxide to each 10,000 parts of air, produced by 
exhalation is of an unhealthful quality. Seven parts 
in 10,000 is ordinarily considered the minimum limit of 
ventilation. The effects of poor ventilation are usually 
shown when the carbon dioxide exceeds six parts in 10,000 
parts. The following rule may be used to determine the 
necessary amount of air that should be supplied to a 
room: Multiply the number of sources of carbon dioxide 
by the amount of carbon dioxide given off from each 
source. Multiply the result by 10,000 and divide by 3. 
This will give the minimum amount of ventilation. For 
satisfactory ventilation divide by 2. Pure air is found 
to contain about 4 parts of carbon dioxide in 10,000. 



96 Notes on Heating and Ventilation 

Ordinary Assumptions for Change of Air. — The amount 
of air necessary is usually determined by allowing each 
person in the room so many cubic feet of air per hour. 
The changes of air ordinarily allowed are given in Table 
XXIV: 



Table XXIV — Change of Air Necessary. 

Hospitals 3,600 cu. ft. per person 

Barracks and workshops 3,000 cu. ft. per person 

Schools 2,400 cu. ft. per person 

Churches, theaters & audience halls.2,000 cu. ft. per seat 

Office rooms 1,800 cu. ft. 

Toilet and bath rooms . . .' 2,400 cu. ft. per flxt're 

Dining rooms 1,800 cu. ft. per person 



These figures in the above table give suflicient air so 
that the air in the room will remain continuously pure, 
even though occupied all the time. When less than these 
amounts are used there is danger, if the buildings are 
very tight, that the rooms may become foul. The figures 
given above are seldom realized in practice, except where 
the fan system of ventilation is used. In school buildings 
using an indirect steam system the amount of air allowed 
per child seldom exceeds 1,000 cubic feet of air per hour. 

Another method that is sometimes used in figuring ven- 
tilation, particularly for smaller buildings, is to allow so 
many changes of air per hour. In rooms seldom occu- 
pied allow the air to be changed about once per hour. In 
living rooms about one and a half to two times per hour. 
In toilet rooms four to five times per hour. In restau- 
rants, where smoking is allowed, from five to six times per 
hour. In extreme cases the change of air is sometimes as 
high as ten times per hour. It is difficult, however, to 
change the air in a room very rapidly without producing 
drafts. 



Notes on Heating and Ventilation 97 

The effects of poor ventilation have been frequently- 
tested in schools where for a short time the ventilation 

has been cut off. The pupils at first 
Effects of Poor complain of being cold, and it is 
Ventilation. found necessary to raise the tempera- 

ture of the room from 70° to 80° and 
even 85° before the occupants of the room are warm. 
This is no doubt due to the reduction in vitality owing 
to the impurity of air, and a lack of oxygen in the lungs. 
After the ventilation has been cut off for a period of 
from 20 to 30 minutes, the pupils begin to complain of 
headache. If the ventilation is cut off much longer it is 
necessary to dismiss some pupils on account of headache. 



98 Memoranda 



CHAPTER VII 



SYSTEMS OF VENTILATION. 

For small residences and small buildings where it is 
not possible to go to any great expense for an elaborate 
system of ventilation, the best form of heating giving 
adequate ventilation is the hot air furnace. In large 
houses where it is not possible to apply the hot air sys- 
tem, the next best system is indirect radiators, either 
steam or hot water. In still larger buildings where the 
flues have a large resistance and it is necessary to supply 
air in large quantities, the only feasible system of dis- 
tributing air is by mechanical means. The usual system 
employed is to draw the air through a series of steam 
coils into a tempered air chamber. In this chamber are 
located the fans. The fan or fans deliver the air through 
heating coils throughout the building. Systems similar to 
this have been used where the coils have been replaced by 
hot air furnaces. 

Systems of ventilation using mechanical draft give 
v6ry satisfactory results if properly installed and allow of 
great latitude in the arrangement of the plant. Before 
taking up the details of the systems of ventilation it is 
well to consider certain fundamental facts in the science 
of ventilation. 

The arrangement of inlet and outlet registers in a room 
should be given very careful consideration. They should 
be so placed as to avoid drafts 

and to insure uniform circula- Air Inlets and Outlets, 
tion throughout the room. 

Their position should be such that the air cannot pass 
directly from inlet to outlet flue. The creation of drafts 
may be avoided by bringing the air in at very low 
velocities, particularly where the air enters so as to strike 
the occupants of the room. The velocity passing through 
the registers should not exceed 200 feet per minute. 



LOFG, 



100 



Notes on Heating and Ventilation 



Where the air is brought in so that it cannot strike the 
occupants of the room the velocity of air through the 
registers may be as high as 400 feet per minute. 

The most satisfactory arrangement for most rooms is 
shown in Fig. 22. In this figure the inlet register is 
shown near the ceiling. The hot air leaving this register 
rises to the ceiling, passes along the ceiling to the cold 




Figure 22. 



window surfaces where it is cooled and drops to the floor; 
passes along the floor and out the vent flue. The inlet 
register is usually located about 8 feet above the floor 
and the outlet register from 4 to 6 inches above the floor, 
just sufficient to avoid dust and dirt being swept into it. 
Where the current of air leaving the inlet register is 
liable to be centered in one point in the room it is well 
to put a diffusing register on the air inlet so that the air 
will be distributed in a number of streams in different 



Notes on Heating and Ventilation loi 

directions throughout the room. This arrangement of 
inlet and outlet registers is the usual one for school 
buildings. It is preferable to have the inlet and outlet 
register on the inside walls opposite the window surfaces 
and both registers on the same wall. This, however, is 
not absolutely necessary. The inlet and outlet registers 
should never be on the outside walls. Where the inlet 




Figure 23. 



register is placed on the floor and the outlet register at 
the ceiling then the air coming from the inlet register will 
pass directly to the outlet register and a large proportion 
of the heated air be lost; in addition there will be very 
little circulation of air in the room, as shown in Fig. 23. 
In rooms for restaurant purposes, where smoking is 
allowed or in smoking rooms or in kitchens, the air must 
be taken off the ceiling as the foul air being warmer rises 



102 



Notes on Heating and Ventilation 



to the ceiling. In this case it is necessary to brl«g the 
ventilating air in at the baseboard, at a very low velocity 
and at a large number of places and take the air out at 
definite points near the ceiling, as shown in Fig. 24. In 
theaters and churches special means must be employed for 
securing ventilation. It is customary to admit the air in 
a large number of places. Sometimes this is done by 




Figure 24. 

means of a large number of small registers placed directly 
under the seats. Care, however, must be used in doing 
this to avoid drafts. Another method is to employ a 
large number of openings around the sides of the room» 
The air is usually taken off near the stage at the lowest 
point in the auditorium. There should be provided in all 
auditoriums some means of taking the air off the ceiling 



Notes on Heating and Ventilation 103 

as oftentimes the heat given off by the occupants of the 
room is more than sufficient to heat the room and in 
addition we have the heat given off by the sources of 
illumination. This heat can be best taken care of at the 
ceiling line, which is naturally the warmest point in the 
room. 

Hot Air Heating. 

In a hot Air furnaee the cold air from the outside is 
passed over heated iron surfaces, usually enclosed in g»J- 
vanized iron or brick walls. 

The space between the walls Design of Hot Air System. 
and hot surfaces of the fur- 
nace is connected to the "outside air at the bottom and 
at the top to the flues leading to the rooms. The amount 
of air circulating through the furnace will depend upon 
the temperature of the hot air leaving the furnace and 
the height and resistance of the flues. In order that the 
air in a room may be quickly replaced by warm air it is 
necessary that the room be provided with a foul air flue. 

A great many of the difficulties that have been experi- 
enced with the hot air system as ordinarily installed, are 
due to the sharp competition in business, which has re- 
sulted in the erection of plants of inferior workmanship 
and design. One of the commonest mistakes is the in- 
stallation of a furnace much too small to do the work 
properly. The result of putting in a small furnace is that 
the fire must be continually crowded so that the heating 
surface is at high temperature and a large amount of the 
heat, of the coal is wasted in excessive stack temperature. 

The hot air system with natural draft should not be 
used in houses where the hot air flues would exceed 25 
feet in length. In very large houses two or more fur- 
naces may be used to avoid excessive pipe resistance. 

Hot air furnaces are as varied in types as are steam 
boilers. They are made either of cast iron or steel. It is 
difficult to decide between the 

merits of these two materials. Cast Hot Air Furnaces. 
iron is less liable to be rapidly de- 
teriorated by rust when the boiler stands in the summer, 



104 Notes on Heating and Ventilation 

but it is more easily broken either by misuse or shrinkage 
strains in the castings. There is no essential difference 
between the metals in their conducting capacity as ap- 
plied in these furnaces. 

It is very important to see that the furnace is so con- 
structed that the joints between the fire-box and hot-air 
chamber are tight, so that the air entering the rooms may 
not be mixed with gases of combustion. This is one of 
the most difl&cult things to prevent in the hot air furnace. 
Joints should be as few as possible and vertical joints 
should be avoided. The introduction of moisture into the 
air passing through the furnace is an important consid- 
eration and will be treated in a separate paragraph. 

The builders rate their 'furnaces at about their max- 
imum capacity. The rating being expressed as the num- 
ber of cubic feet of building volume the furnace will heat. 
In selecting a furnace it is wise to have 25 to 50 per cent 
excess capacity in the furnace over the builder's rating. 

In the hot air furnace we have the fire and hot gases 
on one side of the shell and air on the other side of th3 
shell. Air being a poor medium for the conduction of 
heat it is essential to economy that a hot air furnace 
should have large heating surfaces in proportion to grate 
area. The best manufacturers allow from 50 to 70 square 
feet of heating surface per square foot of grate surface. 

A furnace should be provided with some form of shak- 
ing and dumping grate which is easily cleaned. In addi- 
tion to draft doors admitting air below the grates, the 
furnace is usually provided with a check damper in the 
smoke pipe. The draft door and check damper are ar- 
ranged so that they may be controlled by chains situated 
in some convenient point in the room above. 

It is very important that air after being heated by the 
furnace pass over the surface of a pan of water so that 

it can take up moisture. 

Necessity of Supplying Moist- One pound of air at 32 

ure to Heated Air. degrees F. will hold in 

the form of a vapor .003 
of a pound of water and at 150 degrees it will hold .22 or 



Notes on Heating and Ventilation io5 

about 70 times as much. If then we take air saturated 
with moisture at an outside temperature of 32 degrees 
and heat it up to 150 degrees we have increased its ca- 
pacity for moisture 70 times. On entering the rooms if 
the air has not been given opportunity to take up moist- 
ure it will take it up from the objects in the room. This 
drying effect of the air injures the furniture and wood- 
work and affects the persons occupying the room, produc- 
ing a dry throat and a feeling of cold due to rapid 
evaporation from the skin. 

The usual method of overcoming this is to have a pan 
jailed with water situated in the furnace near the fire box. 
This, however, is the wrong end of the furnace to place 
the pan as the air entering is coolest at this point. The 
water should be added to the air as it leaves the furnace. 
In first-class furnace work every pipe leaving the fur- 
nace has a trough in it, which is filled with water, and 
from this water the air takes up its moisture. 

The cold air supplied to the furnace is usually takeo 
from one of the basement windows and brought to the 
furnace through a tile or wooden duct 
lined with galvanized iron; where a tile Cold Air Duct. 
duct is used it is placed below the level 
of the cellar floor. The cold air should be taken from the 
side of the house that is subject to the prevailing winds. 
It is sometimes desirable to have cold air ducts leading 
to different sides of the house so that the supply of cold 
air may be taken from the windiest side. 

It is well to provide some means of recirculation of 
the air in the house through the furnace. The air for re- 
circulation is usually taken from the hall. If it is desired 
to recirculate partially and take the balance of the air 
from outside, the recirculating pipe should 'be brought 
to the furnace separately, and a deflecting plate placed in 
the air space under the furnace. If this is not done the 
air will come in from the outside and pass up the recircu- 
lating pipe instead of going to the furnace. If, however, 
the recirculating pipe is only to be used when the cold 
air pipe from outside is closed, then the recirculating pipe 



106 Notes on Heating and Ventilation 

can be conducted into tlie cold air pipe directly. In this 
case the cold aii pipe and recirulating pipe must both 
be provided with dampers. The cold air pipe should have 
at least three-fourths of the combin,ed areas of the hot 
air pipes. 

It is a common error to make the recirculating pipe of 
a furnace system too small. The recirculating pipe should 
be not less than three-fourths the area of the cold air 
pipe. It is better to have it equal in area to the cold air 
pipe. 

The furnace should be centrally located, or if the cold- 
est winds come from a certain direction, it can be located 

more on that side of the house from 
Hot Air Flues, which the cold winds come. The hot air 

flues leading from the furnace should be 
as short and direct as possible; long horizontal pipes 
should be avoided. Horizontal pipes should pitch sharply 
towards the furnace, % inch to the foot is good practice. 
All hot air pipes should have nearly equal resistance to 
the passage of the air. The hot air flues should have as 
few and as easy turns as possible. They should never 
be placed in the outside walls. Uptake flues of any kind 
in outside walls seldom draw satisfactorily. The hot air 
flue should enter the room in most cases opposite the 
largest exposed glass surface or some distance from it. 
The circulation of air in the room would be best if the 
hot air enter near the ceiling. The principal objection 
to this is that the register in the wall is apt to blacken 
the wall and it does not allow people to warm themselves 
over it. Floor registers are very objectionable as they 
always serve as receptacles for all kinds of rubbish and 
sweepings. 

Dampers should be provided in all pipes leading to 
rooms above the first floor. If all the registers are pro- 
vided with dampers there is danger of burning the fur- 
nace, due to shutting ofP all the passages for removing hot 
air and preventing circulation in the furnace. It is good 
practice to have no valve in the hall register so one pipe 
will always be open. 



Notes on Heating and Ventilation 107 

The velocity of air for first floor pipes may be calcu- 
lated as three to four feet per second, second floor four 
to five feet per second, 

third floor and floors _ . . ^ -p-r ^ a . -r,, 

, ^ . . r. . Proportions of Hot Air Flues, 

above five, to six leet 

per second. 

The registers should be proportioned so as to give a 
velocity of two to three feet per second on the first floor 
and three to four feet per second on the floors above. The 
effective area of the ordinary register is about 50 per cent 
of the actual area, taking outside dimensions. 

H. B. Carpenter, in a paper before the Society of Heat- 
ing and Ventilating Engineers (Transactions vol. 5, p. 77) 
gives the following rule for finding the cubic feet of air 
passing through pipes per minute: 

To the first floor multiply the area in inches by 1.25. 

To the second floor multiply the area in inches by 1.66, 

To the third floor multiply the area in inches by 2.08. 

It is good practice to figure on changing the air in the 
principal rooms five times per hour in hot air heating. 

The foul air flues should be placed in the inside walls 
and with foul air registers at the baseboard. The reason 
being that the hot air entering the room 
opposite the window surfaces rises to the Foul Air Flues. 
ceiling, passes along the ceiling to the 
windows and is cooled. It then drops to the floor line, 
passes along the floor and out the foul air register. The 
hot air register should be a sufiicient distance from the 
foul air register so that the hot air will not pass directly 
to the foul air flue. A cheap foul air flue can be made by 
having a register in the baseboard opening into the spacj 
between the studs, selecting a space that is open to the 
attic, a ventilator is placed on the attic space and dis- 
charges foul air out of doors. No two rooms should open 
into the same studding space. A still better draft can 
be produced by extending each flue separately by gal- 
vanized iron pipe to the ventilator. If no ventilating 
flues are provided, it is very difficult, especially if the 
house is tight, to get a proper circulation of hot air, from 



108 Noi^Es ON Heating and A^entilation 

the furnace; (you cannot put hot air into a room if there 
is no provision for taking cold air out.) 

A fireplace makes one of the best forms of foul air flue. 
In a house well provided with fireplaces, it is often not 
necessary to provide any other foul air flues. 

The size of hot air flue, vent flue, hot air register, 
heating surface and grate surface in the furnace is giv- 
en in Table XXV. This table 
Greneral Proportions of is given for rooms of average 
Hot Air System. proportion and under average 

conditions. 



Table XXV — Proportions of Hot Air Heating System. 


Contents of 


Room in Cu. 


Ft 




500 


1,000 


1,500 


First Floor — 

Diameter hot air flue, sq. in 

Diameter foul air flue, sq. in 

Second Floor — 

Diameter hot air flue, sq. in. 

Diameter foul air flue, sq. in 

Grate area in furnace, sq. in 

Heating surface in furnace, g 






. 6 
. 6 

. 6 
. 6 
. 25 
. 10 


8 
8 

7 

8 

50 

20 


9 
9 

8 
9 

75 

30 














sq'.'fV.' 




2,000 


2,500 


3,000 


3,500 


4,000 


5,000 


6,000 


8,000 


10,000 


10 

10 

9 

10 

100 

40 


11 
11 

10 

11 

125 

50 


12 
12 

11 

12 

150 

60 


13 
13 

11 

13 

175 

70 


14 
14 

12 

14 

200 

80 


16 
16 

14 
16 

250 
100 


17 
17 

15 

17 

300 

125 


20 

20 

18 

20 

350 

160 


24 
24 

20 

24 

400 

200 



The following assumptions have been made in the above 
table. Temperature outside air degree. Temperature 
of air in the room 70 degrees. Changes of air in the room 
three times per hour. 

Velocity of air in hot air flues, 1st floor 3 ft. per second. 

Velocity of air in hot air flues, 2nd floor 4 ft. per second. 

Velocity of air in foul air flues, 1st and 2d floors 3 ft. 
per second. 



Notes on Heating and Ventilation io9 

Temperature of air entering the room 160 degrees. 

Proportion of grate surface to heating surface 1 to 60. 

Pounds of coai burned per square foot of grate surface 
per hour 2.5. 

The temperature of the rooms should be regulated by 
the drafts of the furnace as much as possible. The heat- 
ing surfaces of the furnace 
should never be brought to a _, ^. - ^ 

red heat. If it is necessary to Suggestions for Operating 
,.,.,, ,, "^ Hot Air Funia<jes. 

do this to keep the rooms 

warm, the furnace is too small. 

Ashes should be frequently removed from the furnace as 
an accumulation of ashes may burn out the grate. Never 
shake the fire more than is necessary to expose the red 
coals to the ash pit. The furnace should be cleaned at 
least once a year. The water pan of the furnace should 
be kept full of water. 

ROUGH RULES FOR HOT AIR SYSTEM. 

1. The volume of the house divided by 50 equals square 
feet of heating surface in furnace radiator. 

2. The volume of the house divided by 20 equals the 
number of square inches of grate area in the furnace. 

3. Divide the volume of the room by 20 and the square 
root of the quotient will be the diameter of the furnace 
pipe for first floor room. For second fl.oor rooms divide 
the volume by 25 and the square root of the quotient will 
be the diameter of the furnace pipe. 

Example of Hot Air System. — As an example of the hot 
air system applied to the ordinary dwelling, take the 
same house that was used as an example of direct steam 
heating. The heat lost from the room.s would be the 
same as in the case of direct steam. As an exam^ple of 
an individual room take the parlor. 

From Table XI we see that the volume of the parlor is 
1,665 cubic feet and the heat lost 9,450 B. T. U^s per hour. 
In figuring the heating system for the parlor the follow- 
ing assumption will be made. The hot air enters the 



no Notes on Heating and Ventilation 

room at 160°. Cold air enters the furnace at 0°. The 
temperature in the room is 70°. Then the air entering 
the room is reduced in temperature 160 — 70=90°. Each 
pound of air on having its temperature reduced to 90° 
would give up .2375X90=21.4 B. T. U's. Then there will 
have to be introduced into the room to supply heat lost 
from the room 9,450-^21.4=442 pounds of air per hour. 
At atmospheric pressure a pound of air occupies approxi- 
mately 13 cubic feet, hence 442 pounds of air is equal to 
5,746 cubic feet. This is the amount of air which must 
be delivered to the room per hour; 5,746 cubic feet of air 
per hour is equal to 1.6 cubic feet per second. Allowing 



Table XXVI— Heat Losses and Ventilation. 

FiKST Floor. Cub. ft. B. T. U. B. T. U. Cub.Ft.In pipe 

Parlor 1,665 9,450 16,750 5,750 10 

Sitting room... 2, 100 7,035 12,500 4,290 9 

Dining room. . .1,640 7,350 13,000 4,480 9 

Kitchen 1,610 10,300 18,300 6,150 10 

Hall 1,210 7,035 4,290 9 

Second Flooe. 

West chamber. .1,320 10,050 17,800 6,100 9 

Alcove 810 7,500 13,450 4,600 9 

South chamber. 1,560 7,035 12,500 4,290 8 

North chamber. 1,440 7,455 13,250 4,560 8 

Bath 410 3,150 5,600 1,920 6 

East chamber.. 880 5,250 9,300 5,670 9 

Front hall 885 2,730 4,850 2,960 6 

Back hall 360 5,040 8,950 5,450 8 

146,250 



a velocity of 3 feet per second, the area of the pipe would 
be 1.6-:-3=.53 square feet, which is equivalent to 76 
square inches or approximately the area of a pipe 10 
inches in diameter. To warm the air going to the parlor 
would require 442 X. 2376X160=16,750 B. T. U's. In a 
similar way the same quantities have been calculated for 
tho other rooms. Except that for the second floor room, a 
velocity of 4 feet per second has been allowed. 



Notes on Heating and Ventilation in 

Column 4 of Table XXVI shows the heat which is left 
by the air in the room. Column 5 shows the heat used to 
warm the room. The difference between these two columns 
is the heat lost up the ventilating flues. This loss should 
not be charged against the hot air furnace but should be 
considered as the loss that must be charged to ventilation. 
This loss is about 44% if the temperature of the outside 
air is at 0°. As the temperature of the outside air in- 
creases proportionately more heat enters the room and 
this loss becomes less. During the average winter weather 
the outside air is 35°, in which case the per cent of loss 
by ventilation, that is through the ventilating tubes, is 
about 30%. 

Summing up column 4 of the table gives the heat re- 
quired to warm the air entering the entire house in zero 
weather or 146,250 B. T. U's. If we assume that 80% 
of the coal goes into the heated air, then there will be 
required from the coal 146,250-^.8=182,800 B. T. U's 
per hour. A good anthracite coal contains about 13,500 
B. T. U^s; then in zero weather this house would use 
182,800-hl3,500=il3% pounds of coal per hour. As the 
average loss from a house during the heating season is 
approximately 50% of the loss during zero weather, the 
average consumption of coal in this house for the heating 
season would be 13.5 X. 5=6.75 pounds of coal per hour. 
Assuming the furnace to be operated 24 hours per day 
and 150 days per year, the coal consumption for this 
house wouM be 6.75X24X150^2,000=12.2 tons. Fig. 24 
shows a cross section of a house with the hot air system 
installed. 

FAN SYSTEM OF HEATING. 

Where it is necessary to introduce large quantities of 
air into a building for the purpose of ventilation a 
natural system of circulation is out of the question and it 
is necessary to force the air into the building by some 
mechanical device. This is usually done by means of a 
steel plate blower which delivers the air with sufficient 
pressure to force the air into all rooms in the building. 



112 Notes on Heating and Ventilation 

The pressure required in the average building does not 
usually exceed one-quarter ounce. The mechanical system 
of ventilation has the additional advantage that its oper- 
ation is entirely independent of the heating of the build- 




Figure 24. 



ing and the building may be ventilated as easily in the 
summer as in the winter. The natural system of ventila- 
tion depends entirely upon the air in flues being heated 
and during the summer periods the system is inoperative. 



Notes on Heating and Ventilation 113 

There are two general schemes of fan heating, one in 
which the air is heated to a temperature higher than that 
in the room, so that it furnishes enough heat to supply the 
windows as well as to furnish 

heat lost from the walls and Systems of Fan Heating, 
air for ventilation. In the other 

system the heat loss from walls and windows is supplied 
by direct radiation situated in the room and the fan 
supplies only the necessary amount of air for ventilation. 
In the latter system the air for ventilation is supplied at 
about the temperature to be maintained in the room. The 
first system, in which all the heat is supplied by means of 
a fan, is most applicable in buildings that must be heated 
and ventilated both night and day. Hospitals and asy- 
lums are buildings of this class. It has certain disadvan- 
tages, however. When a room has very large glass sur- 
faces it is almost impossible with this system to prevent 
strong, cold drafts coming down along the window sur- 
faces. The system is in many cases wasteful. In order 
to heat a building it is often necessary to admit more 
air than is required for the purpose of ventilation, as all 
the heat put into the air to raise the temperature of the 
outside air to the temperature of the room is lost. On the 
other hand, this system requires but one system of heat- 
ing, which makes it less expensive to install. 

The second system mentioned, where direct radiation 
and a fan are both used, is most applicable in buildings 
that require ventilation only part of the time. Schools, 
factories, office buildings are buildings that may be in- 
cluded in this class. While the buildings are filled with 
occupants the fan system is operated; as soon as the occu- 
pants leave the building the fan system is closed and the 
building kept warm by means of direct radiation. The 
building is thus kept warm at a minimum expenditure for 
fuel. There is no necessity of introducing into the build- 
ing more air than is necessary for ventilation. But the 
system is expensive to install as it involves installing two 
separate systems of heating. It is being more and more 



114 Notes on Heating and Ventilation 

favorably considered, however, in connection with the 
class of buildings mentioned. 

The usual arrangement of the fan system is shown in 
Fig. 25. The air is drawn first through a series of tem- 
pering coils shown at A. Then it enters a tempered air 

chamber in which is located the 

General Arrangement of fan. This delivers the air 

the Fan System. through a series of heating 

coils B into the hot air chamber. 
From this hot air chamber the individual rooms in the 
buildings take their heat. The tempered coils are usually 
designed to heat the air to about 70°. The fan takes this 
air at 70° and pases it to the heating coils. After leav- 
ing the heating coils the temperature of the air is from 
130° to 140°. Where the air is used for ventilation only 
the heating coils are omitted and the air is delivered by 
the fan from the tempered air chamber directly to the 
room. 

The quantity of air to be supplied to each room will 
depend upon the system of heating employed. If the 
heating is done entirely by fan enough air must be ad- 
mitted so that the heat left by 
Quantity of Air to Be the air will be sufficient to heat 
Supplied. the room. In audience and school 

rooms the amount of air neces- 
sary to supply proper ventilation is usually sufficient for 
heating. In offices and living rooms more air will have 
to be supplied in order to heat the room than would be 
necessary for purposes of ventilation. Eoughly speaking, 
if the number of cubic feet of air supplied to the room 
per hour is four times the cubic contents of the room the 
room will be heated, providing the air be supplied at not 
less than 140°. In a system where direct radiation is 
used to supply losses from walls and windows only 
enough air is introduced to supply the necessary ventila- 
tion. The amount of air necessary can be determined by 
rules previously given under the head of Ventilation. 



Notes on Heating and Ventilation 115 

In most cases the type of fan known as the steel plate 
blower is best adapted to the work of fan heating. The 
theory of this fan has been discussed by Weisbach and 
Lindner in their treatises, also 

by various writers in the Trans- Size, Speed and Horse- 
actions of the Society of Heat- power of Fan. 
ing and Ventilating Engineers. 

The results derived are difficult of application. The fol- 
lowing general statement may be made, however. The 
discharge capacity of a fan depends upon the speed of 
the fan tips, the size of the fan blades, and the size of 




Figure 25. 



the discharge openings. As the discharge opening of the 
fan is decreased the velocity of the air leaving the fan 
increases and the pressure of air in the fan case increases 
until we get to the maximum pressure that can be pro- 
duced by a certain velocity of fan tips. This will occur 
when the area of the outlet equals the effective area of 
the fan blades. This is the point at which the fan deliv- 
ers the maximum amount of air corresponding to the 
pressure for a given speed. If we further reduce the 
discharge outlet the pressure in the fan case remains 



116 



Notes on Heating and Ventilation 



constant, the quantity of air discharged is reduced and 
the power to drive the fan is reduced. 

The theoretical relations connecting the pressure of 
the air, the quantity of the air delivered, power to drive 

Table XXVII — Fan Capacities. 

Speeds. Capacities and Horse Powers of "A B C" Steel Plate Fans of 
V'arying Revolutions. 



R.P.M. 


FAN 


80 


60 


70 


80 


90 


100 


110 


120 


140 


160 


180 


200 


220 


240 




Per V. 


VW 


942 


1100 


1257 


1414 


1571 


172$ 


1S85 


2200 


2.513 


28.<?7 


8141 


84,55 


S769 




Air v. 


R'y) 


820 


057 


109-2 


vm 


1307 


1503 


1040 


It 15 


-2182 


2459 




3005 


8-279 


100 


Fres. 


.017 


.025 


.034 


.OU 


.055 


.068 


.US2 


.1(X) 


.134 


.175 


.231 


.-273 


.885 


.401 




Cu. Ft. 


fi82 


11-21 


1870 


2652 


8840 


5475 


6895 


95{>5 


14916 


21750 


80221 


41608 


5,5201 


71941 




H. P. 


.150 


;222 


.370 


.476 


.672 


1.01 


1.3/ 


2.03 


3.46 


5.47 


7.7 


12.0 


17.1 


25.1 




Per V. 


P81 


1178 


1375 


1571 


1768 


low 


2160 


23.56 


2750 


3141 


35«3 


39:^ 


4.S18 


4711 




AirV. 


K.=W 


1025 


1596 


1.S66 


1538 


1707 


1S79 


■mnj 


28'.!0 


•27'24 


8073 


8415 


.37.5fi 


4038 


125 


Pres. 


.027 


.089 


.053 


.060 


.0S9 


.108 


.1-32 


.1.5S 


.212 


.-276 


.3.50 


4,35 


5?5 


.6-26 




Ctt. Ft. 


KWl 


\m 


?3.'W 


315,^ 


4309 


6844 


".'^^i. 


11945 


1S645 


27170 


37767 


s-^oio 


68997 


99910 




HP. 


.175 


.284 


.439 


.588 


.934 


1.34 


2.06 


2.90 


5.00 


8.15 


12.5 


19.8 


29.2 


43.5 




Per V. 


1177 


1413 


1650 


1P,<^ 


2121 


2356 


2592 


Z«7 


3C00 


8770 


4240 


4711 


.5182 


5653 




Air V. 


1025 


1230 


1432 


1640 


1845 


2(U4 


2-255 


24t;C' 


-2870 


8-.^) 


S688 


409;^ 


4500 


49-28 


150 


Pres. 


.039 


.056 


.075 


.100 


.130 


.160 


im 


.230 


.800 


.400 


.503 


.626 


.758 


.90* 




Cu. Ft. 


1023 


IfiSl 


»«15 


3979 


5760 


8110 


tsSK) 


14360 


-2'2;r,-4 


32610 


453-25 


62412 


8-2811 


10812C 




H. P. 


.200 


.325 


.531 


.756 


1-27 


1.86 


2.74 


3. to 


7.-22 


11.3 


19.6 


S2.1 


46.2! 68.6- 




PerV. 


1374 


1649 


1925 


2200 


2474 


2749 


8024 


•3-297 


38.50 


4380 


i947 


,549.^. 


6046 


6596 




AirV. 


1195 


U34 


1674 


1914 


'21.52 


•2390 


2630 


2868 


3350 


88'26 


4303 


4781 


,5'260 


574? 


175 


Pres 


;053 


.076 


.104 


.134 


.172 


.-212 


.258 


.^IW 


.420 


..5.54 


.687 


.84X 


1ir2 


1.21 




Cu Ft. 


1194 


1962 


3-274 


46-22 


67-29 


9.594 


11200 


16715 


26100 


.<W>43 


528,<n3 


72814 


966-<>6J 


126089 




HrP. 


.225 


.893 


.617 


1.01 


1.74 


2.46 


3.55 


5,52 


9.91 


17.3 


27.9 


44.2 


67.1 


1-33.0 




PerV. 


1570 


^m 


2200 


2511 


2828 


8142 


8456 


8770 


4400 


5026 


.56.54 


6282 


6910 


753S 




M^. 


1366 


1640 


1915 


2187 


2460 


2787 


3007 


3280 


88;;o 


4875 


4918 


.54/>5 


6011 


655S 


200 


Pres. 


.069 


.101 


1.34 


.175 


.-2-25 


-274 


.333 


.392 


.537 


.700 


fOS 


1 12 


134 


J59 




Cu. Ft. 


1.S64 


2242 


3740 


5304 


7690 


1(»60 


128S0 


191.50 


29850 


435'20 


oOU2 


8.3231 


1W422 


14S9«T2 




H. P. 


.262 


.478 


.855 


1.26 


2.05 


3.16 


4.69 


7.01 


13.3 


'23.7 


39.2 


62.1 


96.« 


154.5 




Per V. 


1766 


21 ?0 


2475 


2829 


.3182 


.1.5,34 


8888 


4241 


4950 


.56.54 


■6360 


7065 


7774 






AirV. 


1538 


1R44 


21,53 


2459 


2767 


£073 


3383 


86^ 


4305 


4919 


5533 


6148 


6762 




22a 


Pres. 


.0,S7 


.126 


.172 


.225 


.285 


.351 


.421. 


.507 


.690 


.fcOl 


114 


1.41 


1.69 






Cu. Ft. 


15.S4 


2.n23 


4207 


5969 


8655 


12334 


14385 


21500 


30560 


48680 


68000 


a3634 


124217 






H. P. 


.300 


.581 


1.03 


1.57 


2.61 


4.09 


5.95 


929 


17.0 


31.1 


52.8 


87.9 


142.5 




. 


Per V. 


1963 


23.55 


2750 


3143 


85.^5 


3927 


4320 


4712 


5.500 


6283 


7067 


7,8.52 








Air V, 


1708 


204A 


2392 


2734 


8070 


3413 


37.58 


41(X) 


4780 


.54.50 


6148 


6840 




"250 


Pres. 


.109 


.056 


.213 


.280 


.360 


4;i0 


..5'20 


m) 


.,Sf,0 


1 12 


148 


1.73 






Ca. Ft. 


1706 


2793 


4675 


63.32 


9600 


13705 


16000 


23<S0 


37310 


54200 


755.58 


104036 






H. P. 


.875 


.684 


1.22 


1.79 


3.32 


4.97 


744 


11.6 


^2.5 


41.2 


71.7 


i-21.4 






Per V. 


2159 


?-i91 


.3025 


3457 


3880 


4319 


4731 


.51P.3 


6050 


con 


7774 








AirV. 


1878 


22.'i.S 


2632 


8008 


3383 


8755 


40-0 


4.507 


5-263 


6013 


6763 




£75 


Pres. 


.131 


.189 


,258 


.837 


.426 


.526 


.6'23 


.7.56 


1.04 


1..35 


1.71 






Cu. Ft. 


1X76 


8083 


5142 


V294 


10578 


1.5773 


17394 


26278 


41O20 


58:^28 


.h;^104 






H.P. 


.436 


.821 


1.45 


2.35 


3.1>2 


6.0;> 


9.09 


14.5 


'29.4 


54.7 


89.3 






Per V. 


%^^^ 


28-26 


3300 


3771 


4242 


4712 


.^184 


56.54 


6600 


7.5.39 








AirV. 


20.50 


24.58 


ZS75 


3280 


36,S5 


41 (K) 


4510 


49C0 


.5745 


6.555 




300 


Pres. 


:1»M) 


.225 


..S02 


.401 


..5-?0 


.680 


.760 


.910 


1.26 


1.62 






Cu. Ft. 


2016 


S363 


5610 


7957 


115-20 


16^50 


19200 


28800 


44750 


636-29 






H.P. 


.500 


.975 


1.73 


2.86 


4.63 


7.44 


11.4 


18.1 


375 


69.3 






PerV. 


2747 


8297 


8850 


4,399 


4949 


.5447 


6018 


fi.597 


7700 








Air V. 


2399 


2,'^3 


3.345 


3,H^27 


4-295 


4770 


fi-262 


5724 


66,S() 


NOTE 


S50 


PVes. 


.216 


.306 


.418 


.5.50 


.69-J 


.8.50 


970 


1.25 


1.68 


Tliese figures guaranteed to 




Cu Ft. 


23S7 


8923 


6.545 


92^2 


1.3410 


19110 


22395 


3.-^400 


.52206 




H. P 


.663 


1.-28 


2.88 


3.89 


6.65 


10.7 


17.2 


28.3 


55.8 


• be correct with the resistance 




PerV. 


3140 


376S 


4400 


5028 


56.56 


6X82 


6912 


7540 




ordinarily found in heating 




Air V. 


2732 


3278 


8880 


A?,'\ 


49-26 


.5470 


6013 


6560 


worK. 


400 


Pres. 


.277 


.899 


..546 


.713 


.904 


1.14 


1.42 


1.63 






Cu. Ft. 


2729 


4384 


7480 


106-20 


15400 ' 21950 


-2,5574 


38300 






H.P, 


.750 


1.70 


3.19 


5.04 


9.S4 1 15.3 


25.2 


39 2 





Notes on Heating and Ventilation 



117 



the fan and the speed can be stated briefly as follows: 
The quantity of air delivered is proportional to the per- 
ipheral velocity of the fan tips. The pressure produced 



Table XXVIII- 



Fan Efficiency Under Varying Pressures. 

Steel Plate Fans of 



Speeds, Capacities and Horse Powers of "A B C 
Varying Pressures. 



PRESSURES. 


Hoz. 


%oz. 


Koz. 


1 oz. 


IH oz. 


VA oz. 


IKoz. 


2. or. 


2'/» oz. 


3 oz. 


50 


CU. FT. 

R. P. M. ; 

H. P. 


2740 
380 
.80 


3900 
.540 
1.60 


4760 
6.59 
2.66 


5490 
760 
3&5 


6090 
847 
5 32 


6700 
930 
6.65 


73.50 
1004 

8.22 


7750 
1075 
10.25 


8*50 
1200 
14.38 


9520 
1320 

18.85 


60 


CU. FT 

R. P. M. 

H. P. 


3.iS0 
317 
103 


5040 
449 
2.05 


54fK) 
549 
3.42 


7100 
633 
4.95 


7910 
706 
6.^ 


8700 

776 
8.54 


9410 

838 

10.60 


10200 
895 
13.2 


11210 
1000 
18.45 


12330 
1100 
24.3 


70 


CU. FT. 

R. P. M. 

H. P. 


5220 
271 
1.51 


7350 
383 
3.02 


9050 
471 
5.04 


10400 
542 
7.30 


11600 

605 

10.10 


12700 

663 

12.Ga 


13750 

716 

15.60 


14750 

768 

19.40 


16500 

857 

27.20 


18000 
938 
85.7 


80 


CU. FT. 

R. P M. 

H. P. 


630 
238 
1.82 


8900 
336 
3.05 


10940 
412 

6.08 


125.50 


14000 

5.-50 

12.15 


15350 

.580 

15.20 


16600 
627 

18.85 


17300 

672 

23.40 


19890 

750 

33'.80 


21920 

825, 
43.2' 


90 


CU. FT. 

R. P. M. 

H. P. 


78.50 
211 
2.27 


U050 
299 
4.53 


13600 
366 
7.56 


15000 

421 

11.00 


174.50 

470 

15.10 


19100 

515 

18.90 


20650 

557 

23.40 


22100 

566 

29.10 


247.50 

666 

40.70 


27300 
734 
53.5 


100 


CU. FT. 

R. P. M. 

H. P. 


9.540 
190 
2.76 


13.500 
268 
5.52 


16500 
329 
9.20 


19050 

380 

13.35 


21300 

424 

18.42 


23.';oo 

464 
23.00 


25200 

502 

28.60 


27000 

537 

35.60 


30500 

600 

49.60 


33fiOO 
659 
65.2 


110 


CU. Fl. 

R. P. M. 

H. P. 


11870 
173 
3.43 


16700 
'244 
6.85 


20800 

300 

11.44 


236C0 

345 

16.60 


26400 

385 

22.60 


28900 

422 

28.60 


81300 

456 

35.50 


33500 

488 
44.00 


375C0 
546 
61.7 


41200 
600 
81.2 


]20 


CU. FT. 

R. P. M. 

H. P. 


15O0O 
1.59 
4.32 


21000 
224 
8.65 


25840 

274 

14.40 


29700 

816 

20.60 


33200 
3.54 

28.80 


36400 

387 

36.00 


39400 

418 

44.00 


42-200 

448 

55.45 


47100 
.SOO 

77.7 


51800 

5.50 

l'D2.1 


140 


CU. FT. 

R. P. M. 

H. P. 


19800 
136 
5.72 


27900 

192 

11.42 


34200 
. 2:-,5 
19.00 


39400 

271 

27.60 


44000 

302 

S8.10 


48200 

331 

47.60 


51200 

357 

59.00 


55800 

883 

73.30 


639C0 

439 

102.7 


68400 

470 

125.5 


160 


CU. FT. 

R. P M 

H. P 


.2.5050 
118 
7.29 


35600 

168 

14.60 


43700 

206 

24.32 


.502.50 

237 

35.20 


56150 

•265 

43.00 


61500 

290 

160.75 


66500 

314 

75.30 


71250 

336 

93.50 


79200 

373 

134.0 


87500 

412 

172.0 


180 


CU. FT. 

R. P. M. 

H. P. 


31410 
106 
9.07 


44200 

149 

18.13 


54300 

183 

30.24 


62700 

211 

43.80 


69700 

235 

60.48 


76700 
259 
75.5 


82700 
279 
93.6 


88400 

298 

116.20 


99000 

334 

131.0 


10S400 

866 

214.0 


200 


CU. FT. 

R. P. M. 

H. P 


38000 

95 

11.02 


53700 

134 

22.20 


66000 

165 

36.80 


75700 
189 
53.3 


849.50 
212 
73.5 


93000 
2:J2 
92.0 


100500 

251 

114.0 


107200 

268 

141.5 


120000 

300 

198.5 


134000 

830 

261.0 


220 


CU. FT. 

R. P. M. 

H. P. 


46800 

87 

13.48 


66300 

1-23 

27.00 


80900 

1.50 

44.90 


93200 

173 

65.10 


104000 
193 
89.6 


113500 

211 

112.0 


123300 

229 

139.0 


131400 

244 

173.0 


147100 

274 

243.0 


161.500 

300 

318.0 


240 


CU.'FT. 

R. P M. 

H. P. 


56400 

80 

16.10 


79O0O 

112 

32.30 


96.500 

137 

.53.80 


112000 

1.59 

78.00 


124800 

177 

107.4 


136S00 

194 

134.0 


147400 

209 

106.0 


15SO00. 

224 

206.0 


176100 

250 

290.0 


194000 

275 

882.0 



is proportional to the square of the peripheral velocity of 
the fan tips and the power necessary is proportional to 
the cube of the peripheral velocity of the fan tips or to 



118 Notes on Heating and Ventilation 

the quantity of air delivered. Mr. M. C. Huyett gives 
the following approximate rule for finding the capacity 
of a fan: The quantity of r^ir in cubic feet delivered per 
revolution is equal to one-third the diameter of the fan 
wheel multiplied by the width of the blades at circumfer- 
ence, multiplied by the circumference of the fan wheel. 
All dimensions expressed in feet. 

Professor E. C. Carpenter gives the following rule for 
determining the horsepower required by the fan: The 
horsepower required for the fan is equal to the fifth power 
of the diameter of the fan wheel in feet multiplied by the 
number of revolutions per second, divided by 1,000,000 
and multiplied by one of the following coefficients — for 
free delivery, 30; for delivery against 1-ounce pressure, 
20; for delivery against 2 ounces pressure, 10. The best 
method of obtaining the horsepower to drive a fan and 
the capacity of the fan is by reference to the blower com- 
panies ' catalogues. Some companies have published cata- 
logues which are obviously wrong. At the present time, 
however, the American Blower Company, of Detroit, have 
published in their catalogue tables that are very satisfac- 
tory. 

Table XXV gives the speed, capacity and horsepower 
required for various sized fans. 

Table XXVI gives similar results for different sized 
fans at varying pressure. 

The table should be made use of in the following man- 
ner: Having determined the quantity of air required for 
the entire building, we select from the table a fan which 
would give the proper capacity. In doing this three 
things must be considered. The fan must have sufficient 
capacity to deliver the amount of air required. It must 
deliver this air with the minimum horsepower and it must 
rotate with sufficient speed to produce a pressure in the 
fan system sufficient to overcome the resistance of the 
piping. It is always possible to select either a small fan 
driven at a high speed or a large fan driven at a low 
speed, both of which will deliver the same capacity of air. 



Notes on Heating and Ventilation 119 

A large fan may be driven at so slow a speed that it will 
not produce sufficient pressure to overcome resistance of 
the air flues. Choose the largest fan that, driven at suf- 
ficient speed to overcome the resistance of the air flue, 
will deliver the proper quantity of air for the purpose of 
ventilation. As an example: Suppose we wish to deliver 
to a building 10,000 cubic feet of air per minute. Kefer- 
ring to the table, we see that we may use an 80-inch fan 
driven at 400 revolutions, in which case there would be 
required 5 horsepowers to drive the fan and the pressure 
produced would be .713 ounce. Or we might use a 120- 
inch fan driven at 125 revolutions per minute, in which 
case the power required to drive the fan would be 2.9 
horsepowers and the pressure produced would be .153. 
In the first case the fan is small and being driven at high 
speed the pressure produced is far more than necessary 
to overcome the resistance requiring an excessively large 
horsepower to drive it. In the case of the 120-inch fan 
while the horsepower is much lower the pressure is insuf- 
ficient to overcome the ordinary resistance. For ordinary 
purposes the pressure should be about .25. Keferring 
again to the table, we see that the 100-inch fan driven at 
200 revolutions per minute would require 3.15 horsepowers 
and produce a pressure of .274. This would be about the 
proper size of fan to select. The pressure required to 
overcome the resistance of the building depends very 
largely upon the capacity and design of the flues and 
the resistance of these flues is largely a matter of judg- 
ment and experience. 

Heating Coils. — The determination of the proper quan- 
tity of heating coil to raise the air to a given temperature 
will depend primarily upon the amount of heat given off 
per square foot of heater coil. 

Table XXIX is obtained from the results of experiments 
made by the American Blower Company, of Detroit, and 
shows the condensation and heat given off by ordinary 
pipe heater coils under different conditions. Knowing 
the heat given off by the coil per square foot, under given 



Table XXIX — Condensation and Heat Given Off by- 
Heater Coils. 



o. 






C/3 


o 


TEMPERATURE AIR ENTERING COIL O'^-IO^ 


'o 


Velocity of Air 


Velocity of Air 


Velocity of Air 


Velocity of Air 


I 


C 


1000 feet per 


1250 feet per 


1500 feet per 


1700 feet per 


C/3 
C 

o 


minute. 


minute. 


minute. 


minute. 


iX 


_^ 






- 


,^ 


— 








o 


ation 
efoo 

ds. 


ture 
gcoi 
s. 


rj 0) "^ 


ture 
gcoi 
s. 


ation 
e f 00 

ds. 


ture 
gcoi 
s. 


§8 . 


ture 
gcoi 
s. 


<D 


c/5 ^- C 


a r-.- <u 


en i~ C 


a e oj 


t/i ^- c 


n c <u 


S 2: c 


P3 r- <U 


a 


;^ 


Conden 

per squa 

in pou 


Temper 

air leavi 

degre 


Conden 

per squa 

in pou 


Temper 

air leavi 

degre 


Conden 

per squa 

in Pou 


Temper 

air leavi 

degre 


Conden 

per squa 

in pou 


Temper 

air leavi 

degre 



8 

12 

i6 

20 

24 
28 

32 



2 


2.9 


74 


2.37 


65 


2.56 


60 


2.72 


3 


1.78 


94 


2.1 


82 


2.32 


77 


2.45 


4 


1.53 


114 


1.86 


98 


2.09 


93 


2 25 


5 


1. 31 


130 


1.68 


115 


1.88 


108 


2.05 


6 


1.20 


143 


1-54 


128 


1.77 


122 


1.92 


7 


1. 10 


152 


1-45 


140 


1.70 


134 


1.85 


8 


1.05 




1.40 


148 


1.65 


140 


1.77 



55 
73 

88 

103 
117 
129 
133 






o 
o 

(/) 

<v 
0. 

'5. 
o 

e 

3 

z 



8 

12 
16 
20 
24 
28 
32 



TEMPERATURE AIR ENTERING COIL 40^^-50'^ 



\^elocity of Air 

1000 feet per 

minute. 



Velocity of Air 

1250 feet ber 

minute. 



= 2 

o o • 

^ 2^ C 

(/; w. C 

C « 3 

flj 3 O 

3 ^ - 

a 



U 



3 ^ . 

2 = §i 

^•1 



c o 

O O ; 

^ is 5 

c ^ 3 

a; 3 o 

-a o- a 

c '-^ c 
U5^ 



c:S c 1^ 
»- .3 OJ 

a» >. u 
^•5 



Velocity of Air 

1500 feet per 

minute. 



Velocity of Air 

1700 feet per 

minute. 



c 
00. 


Sig 


SR . 


• - vt- CO 


3 "^ . 


c3 a> "^ 


(/) V- C 


Tempera 

air leavin 

degree 


c^ u C 


C «^ 3 


C rt 3 


o; 3 


<1> 3 


T3 o- a 


73 o" a 


§".= 
u^ 





2i'o 

U- W) (/5 

rt c ^ 

Si > ■ 



W 



^•1 



.75 


91 


2.07 


84 


2.37 


80 


2.52 


.50 


107 


1.80 


100 


2,06 


95 


2.23 


.41 


119 


1.65 


112 


1.89 


107 


2.02 


•37 


133 


1.60 


125 


1.80 


121 


1.90 


.32 


143 


1.50 


137 


1.67 


135 


1.77 


.26 


150 


1.40 


145 


1.56 


142 


1.64 


.14 


158 


1.30 


152 


1.48 


148 


1.52 



78 

93 
105 
119 

133 
140 

147 



Notes on Heating and Ventilation 121 

conditions, the number of square feet of coil surface 
necessary may be obtained in the following manner: 
Multiply the air to be passed per hour by the difference 
between the temperature of the outside air and the tem- 
perature of the air after passing through the coil. Mul- 
tiply this product by .2375. Divide the result obtained 
by 13.3, multiplied by the condensation per square foot 
of surface per hour, multiplied by 966. Let C = conden- 
sation per square foot of coil; V = volume of air in cubic 
feet passing per hour; F = square feet heating surface 
coil should contain; t=temperature outside air; t'=tem- 
perature of air after passing coil; then 
V X .2375 (f— t) 

F= 

13.3 X C X 966 

In most cases the condensation in the tempering coils 
can be assumed at about 2 pounds per hour and in the 
heating coils about 1% pounds. In extreme cases con- 
densation as high as 5 pounds per square foot per hour 
have been reported. 

After determining the number of square feet of surface 
in the heater the heater must be so designed as to allow 
sufficient air area for the pasasge of air through the 
heater coils. The coils as ordinarily arranged are shown 
in Fig. 26. Sufficient area should be allowed in these 
coils for the velocity of air passing. This should not ex- 
ceed 1,200 feet per minute, except where coils are very 
large. Tempering coils should not be less than 12 pipes 
deep. If the heater coils are made very shallow the con- 
densation in the coil is so rapid that in cold weather they 
will hammer. 

The heater coil consists of a cast iron base into which 
is screwed 1-inch steam pipes jointed at the top by nipples 
and elbows. The cast iron base for each section is pro- 
vided with a steam inlet and drip, both connected to the 
cast iron heater base. Most bases are constructed for 
four rows of pipes. Table XXX gives the principal di- 
mensions of the American Blower Company ^s heaters 
with the size of fan regularly used. 



122 Notes on Heating and Ventilation 





Table 


XXX- 


-Fan Dimensions. 




Lineal feet 










Size 


capacity 








Net air 


Reg- 


of fan. 


of l-inch 


Connections. 


space in 


ular 


Steel 


pipe. 


Steam. 


Drip. 


Bleeder. 


sq. ft. 


Disc. 


plate. 


200 


2" 


1" 


%" 


5.4 


30 


80 


300 


2" 


1" 


%" 


7.6 


36 


90 


400 


2" 


1V4" 


%" 


10.7 


42 


100 


525 


2" 


ly^" 


1" 


14.3 


48 


110 


650 


2" 


iy2" 


1" 


17.7 


54 


120 


825 


2y2" 


ly," 


1" 


22.2 


60 


140 


1,175 


2yo" 


iy2" 


1" 


31. 


72 


160 


1.525 


3" 


2'' 


iy4" 


40. 


84 


180 


2,025 


3" 


2" 


ly*" 


52.5 


96 


200 



The success of the fan system depends very largely 
upon the design of the flues. The best form of flue is 

round, the next best form is square, 
Ventilating Ducts, or, if rectangular, as nearly square as 

possible. All turns and branches 
should be made with easy curves. The size of the flues is 
ordinarily determined by the velocity of the air passing 
in the flues. In main ducts of large size a velocity as 
high as 2,000 feet per minute or over may be used. In 
the branch ducts the velocity should not exceed 1,000 to 
1,500 feet. In flues leading to the individual rooms the 
velocity should be from 600 to 1,000 feet per minute, 
depending upon their size. Where the ducts are of small 
size this velocity is often reduced to 400 feet per minute. 
The velocity at the registers should not exceed 300 feet 
per minute except in very large registers so located that 
the current of air entering the room will not strike the 
occupants of the room. In all ordinary buildings, if these 
proportions of air velocities are used the resistance of 
the system will be from two to three-tenths of an ounce 
pressure. In designing the ducts for a fan system short 
bends and tee branches should be avoided. The bends 
should be long and the branches made with Y's. The 
inside radius of the bend should be equal to the diameter 



Notes on Heating and Ventilation 



123 



of the pipe as a minimum and where conditions will per- 
mit, twice the diameter of the pipe. Where branches 
leave the main ducts it is a common practice to place a 
deflecting damper at the bend of the branch. This is 
merely a piece of galvanized iron attached to the point 
of the branch which may be adjusted and fastened so 
that each branch will take its proper supply of air. 
Dampers controlled by the attendants in the building 
should be as few as possible. The reductions in the size 




Figure 26. 

of a flue should be made gradually. The angle of the 
reduction should not exceed 30°. No round pipes less 
than 6 inches in diameter are used, and if rectangular, 
less than 6x8. A common arrangement of ducts is to 
let them radiate from the fan in the form of a tree, with 
trunk and branches. This, however, makes the duct sys- 
tem very expensive and a system having large feeding 
mains similar to a system of steam piping is the one 
more used as it can be designed to give satisfactory re- 
sults. Another very satisfactory method of distribution 
is to force all the air from the fan into a large duct or 
chamber in which the air has a very low velocity. The 
rooms take their air from this chamber by means of 
vertical flues controlled by proper dampers. These large 
chambers are called Plenum chambers. A good example 



124 



Notes on Heating and Ventilation 



of this is shown in the construction of the new Engineer- 
ing building, University of Michigan. In this building 

Table XXXI — Pressure Losses. 

Air.— Loss of Pressure in Ounces per Square Inch per 100 Feet of Pipe of 
Varying- Velocities and Varying Diameters of Pipes. 



Velocity of Ait 






DIAMETER OF PIPE IN INCHES. 






















Feet per 


1 


2 


3 


4 


6 


e 


7 


8 


Minute, 


















Loss OF Pressure ik Oi'mTes. 


600 


.400 


.200 


.133 


.100 


.080 


.067 


.057 


.050 


1,200 


1.6'JO 


.800 


.533 


.400 


.320 


.267 


.222 


. .200 


1,800 


8.600 


1.800 


1.200 


.900 


.720 


.600 


.514 


A^y 


2,400 


6.400 


8.200 


2.133 


1.600 


1.280 


1.067 


.914 


.600 


8,000 


10.000 


5.000 


3.333 


2.500 


2.000 


1.667 


1.429 


1.2.5<3 


3,600 


UAGO 


7.200 


4.800 


3.600 


2.S80 


2.400 


2.057 


1.800 


4,200 




9.800 


6.5.')3 


4.900 


3.920 


3.267 


2.800 


2.450 


4,800 




• 12.800 


8.533 


6.400 


5.120 


4.267 


8.657 


8.2'JO 


6,000 




20.000 


13.333 


10.000 


§.000 


6.667 


5.714 


&000 









DIAMETER OF PIPE IN INCHES 


Velocity of Air 




_ 














Feet per 


9 


10 


11 


12 


14 


16 


18 


20 


Minute. 




















Loss OF Pressure in Ounces. 


600 


.044 


.040 


.osa 


.033 


.029 


.026 


.0^2 


.020 


1,200 


178 


.160 


.145 


.133 


.114 


.100 


.089 


•0^ 


1,800 


.400' 


.360 


.327 


.300 


.257 


.225 


200 


.150 


2,400 


.711 


.640 


.582 


.533 


.457 


.400 


85S 


.820 


3,000 


l.lll 


3 


.909 


.833 







, 


, 


8,600 


1.600 


1.309 


1.200 


1.029 


.900 


.800 


.720 


4,200 


2.178 


1.960 


1.782 


1.633 


1.400. 


1.225 


1.089 


'.980 


4.800 


2.844 


2.560 


2.327 


2.133 


1.829 


1.600 


1.422 


1.280 


6,000 


4.444 


4.000 


3.636 


3.333 


2.857 


2.50e 


2.222 


2.000 









DIAMETER OF PIPE IN 


NCHES. 






Velocity of Air 










1 








Feet per 


22 


24 


28 


82 


86 


40 


44 


48 


Minute. 










i 










Loss of Pres-sure in Ounces. 


600 


.01.3 


.017 


.014 


.OK 


.011 


.010 


.009 


r.008 


1,200 


.073 


.cr.7 


.057 


.050 


.044 


.040 


.036 


.033 


1,8«30 


.164 


.158 


.129 


.112 


.100 


.090 


.082 


.075 


2,400 


.291 


.267 


.239 


.200 


.178 


.160 


.-145 


.138 


8,600 


.6.55 


.OO-J 


.514 


.450- 


.400 


,360 


.327 


.SCO 


4,200 


.891 


.817 


.700 


.612 


,544 


.490 


.445 


,403 


4,800 


1.164 


a.067 


.914 


.800 


.711 


.640 


.582 


.533 


eLoQd 


1.818 


1.867 


1.429 


1.250 


UU 


ism 


.909 


.833 



the corridor on the ground floor has a false ceiling about 
3 feet below the second story floor. This leaves a space 3 



Notes on Heating and Ventilation 



125 



feet high by 12 feet wide extending through the entire 
building. Into this space two separate fans deliver their 
air. The space acts as a Plenum chamber and the indi- 
vidual flues leaving the rooms take their air from this 
Plenum chamber through volume dampers which may be 
set and fastened after the proper position has once been 
determined. 

Table 29 shows the loss of pressure per 100 feet of pipe 
for varying velocities and varying diameters of pipes. 
This table is quite liberal and allows for two ordinary 
90° bends per 100 feet. 




Figure 27. 



Where the building is heated entirely by a fan system 
it is necessary to devise some arrangement by which the 
room may be either furnished with 

hot r-ir or tempered air. In case Air Mixing Systems, 
the room becomes too warm, to 

close off the hot air register would do away entirely with 
ventilation and it is necessary to provide some means of 
introducing tempered air. The method usually used is 
shown in Fig. 26. Where each room is connected both to 
the warm air chamber and to the cold air passage, the 
dampers being connected so that when the warm air is 
turned off cold air is introduced into the room, or vice 
versa. In this case the mixing damper is located near the 
fan and preferably controlled automatically. Another 
system shown in Fig. 27 has entirely separate cold and 
hot air flues which are led to the base of vertical flues 



126 Notes on Heating and Ventilation 

leading to the rooms, at which point there is introduced 
a mixing damper similar to the mixing damper shown in 
Fig. 26. 

The flues for fan systems are ordinarily constructed of 
galvanized iron with double lap joints riveted and sol- 
dered. The ducts should be made 
Materials of Flues. as nearly as possible air-tight. The 

weight of material used for ducts 
depends upon the size of the duct. It ordinarily varies 
from No. 26 to No. 16 gauge. Large ducts are also made 
of sheet iron with close riveting. When ducts are made 
of sheet iron the ducts are painted and then asphalted. 
Where it is necessary to build ducts underground they 
are built of brick or cement. The cement, if anything, 
is preferable to brick, as it does not absorb odors as 
easily and may be plastered to make a smooth job. 
Where possible it is desirable to build the ducts into the 
building itself, making them of permanent material. 
Brick or cement ducts built into the building and so 
arranged that they may be examined and cleaned easily 
are the most satisfactory. Wood is always a bad mate- 
rial to use for ducts and should be avoided. Where it is 
used the ducts are lined with tin, owing to the fact that 
wood usually shrinks, leaving open joints. 

Vent ducts from closets should be carried out of the 
buildings separately from the other vent flues. Where 
these ducts are made of brick they should be lined with 
galvanized iron to prevent the odors from the closet 
being absorbed by the brick. It is very desirable that 
closet vents should be collected at convenient points and 
then exhausted from the building by means of a fan. 
This prevents the odors from the toilet rooms being car- 
ried back into the building. 

Disc fans are used where the resistance to be overcome 

is very slight or in cases where the ducts are very large, 

with easy turns and of very short length. 

Disc Fans. They are extensively used for exhausting the 

air from the vent flues and where the vent 



Notes on Heating and Ventilation 



127 



flues are short and large they give good satisfaction. 
The capacity, speed and horsepower of various sizes of 
disc fans is shown in Table 30. 

Table XXXII— Disc Fan Efficiency. 

Disc Ventilating Fan — Capacities, Speeds and Horse Powers. 
(American Blower Co ) 



Air Veloc- 
ity IN Ft. 

PBR MiN. 


Siie 
Fan 


18 


21 


24 


30 


36 


42 


48 


54 


60 


72 


84 


96 


108 


X2d 


600 


Free 


Cu. Ft. 

R. P. M. 

H.P. 


1060 


.022 


1880 


"1 
048 


, 064 


5772 
140 
067 


7536 

122 
"3 


9540 
110 
143 


11770 

98 

■'77 


16960 
82 
253 


33090 

70 

■345 


30.56 
.450 


38160 
55 

573 


47160 




Heater 


R. P. M. 
.H. P. 


530 
■053 


453 
072 


396 
.094 


3«7 
•.«47 


367 

.a:a 


227 
.388 


«97 
■377 


«78 
.477 


158 
•590 


.^ 


"3 
» '5 


100 
• 5' 


89 
,.91 


81 

235 


700 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


1235 
370 
.025 


1680 
328 

•035" 


aaoo 
380 
• 045 


3400 
330 
.070 


4940 
190 
.110 


..36 


8800 
145 

.178 


11120 

'27 

.227 


13750 
112 

•273 


19760 
.402 


369SO 
.548 


35016 

72 

•740 


44500 

62 

■905 


"1? 

1. 11 


Heater 


R. P. M. 

H. P. 


600 
.07. 


•.ss 


«5 
.126 


.^. 


307 
.283 


266 

• 384 


• S34 
.503 


*o6 
.636 


i78 
,786 


'58 
"3 


132 
« 54 


116 
a. 10 


100 
2.52 


92 

3«4 


800 


Free 


Cu. Ft. 

R. P. M. 

H.P. 


1410 

ill 


1920 

III 


2510 

.III 


'III 
098 


5650 
ai8 
.142 


7700 
187 
.192 


10300 

464 
■251 


i27io 
'45 
• 3'7 


IS7'0 
'3' 
•392 


33600 
110 
.562 


30400 


40.50 
1.00 


S0900 

73 

1 37 


63800 

66 

» 57 




Heater 


R. P. M. 
H.P. 


70s 
.106 


604 

149 


.;g 


424 
.>94 


.m 


302 

•5'9 


265 
•756 


234 
•957 


312 
1.18 


'78 
1 71 


152 
2.32 


'34 
3.20 


U8 
383 


107 

4 73 


900 


Free 


Cu. Ft 

R. P. M. 

H. P. 


1584 
490 
■.048 


2160 
425 
.06s 


3826 
368 
.085 


4410 

285 

>32 


Hit 
.-.90 


«6so 

2tO 

•258 


11304 

•» 


143'0 

164 
.428 


•S30 


25443 
123 
,762 


34642 
106 

1.04 


45234 
. 93 
•'•35 


57250 

82 

1.72 


70650 
..It 


Heater 


R.P.M. 
H. P. 


792 
■ 143 


770 
•J95 


595 

254 


46. 
.397 


398 
•572 


340 
.780 


298 

1.02 


365 
1.29 


236 
'59 


199 
4^9 


'73 

3.12 


'50 
407 


132 
5 'S 


6'§ 


xooo 


■ 
Free 


Cu. Ft. 

R. P. M. 

H. P. 


1770 

545 
057 


2400 

.X 


3?40 
406 
•^04 


4900 
328 
142 


7060 
27s 
•233 


9610 
234 
•317 


12560 
205 

•413 


159CO 
181 
.520 


•'ill 
•647 


38270 

'36 

.933 


38480 
120 
1.37 


50265 
'03 
1.66 


63600 

9- 

2.09 


7S540 
2.56 




Heater 


V:^'- 


883 
.204 


760 
.576 


'S 


.III 


:t^i 


378 
1 ti 


332 

'45 


.293 
i.§3 


308 
3.26 


220 
326 


'94 
4 44 


'67 
S 77 


.'47 
7 33 


1^2 

9.05 


X200 


Free 


-Ctf. Tt. 

R, P. M. 

H.P. 


2112 - 

654 
.101 


2880- 


■.3768- 


.5880 
.It 


8472 

33° 
^•405 


1 1541 
280 
•55° 


15072 
245 
•716 


19100 

2l8 

.910 


33566 
196 
' '3 


33900 
164 
1.62 


46176 
140 


60312 
124 
2.87 


76300 
Vio 
363 


94240 




Heater 


R. P. M. 
H.P. 


»o59 
.300 


912 
•409 


.,788 
534 


636 
.832 


534 

1.20 


,% 


.396 
2.14 


35» 
2 70 


322 
3 37 


264 
4.85 


6 60 


200 
,863 


«76 
10.8 


iS 


1400 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


2475 
767 
•133 


1i 


4400 
57° 
.23^5 


•?68 


'IS 

•530 


13470 
327 
.721 


•942 


33270 
254 
1..9 


27500 
■ 230 
'55 


39600 
190 

2.12 


53900 

164 

•2.89 


70300 

'44 

, 3 77 


88950 
12S 
4 77 


109500 
589 




Heater 


R. P. M. 
H. P. 


■3? 


1064 

.660 


.III 


742 

'■35 


623 
'•95 


3.64 


3 46 


4.38 


376 
S-40 


308 

^•88 


TO. 6 


234 

.38 


205 
'f-S 


21.6 


1600 


Free 


Cu. Ft. 

R. P. M. 

H.P. 


2830 

'•11 


3850 
750 
.252 


5000 
656 

.330 


78.0 
526 
.5»5 


•742 


15400 
375 
I 01 


2C050 
332 

'34 


35400 

.t 


31400 
2'^ 


45200 

B20 
2.97 


61500 
I&8 
4 05 


80000 


,0.300 






Heater 


R. P. M. 
H.P. 


1412 

•735 


1216 


1050 
» 3.' 


848 
2 04 


712 

2.94 


603 
4.00 


S37 
523 


6'g 


8*:? 


35' 
11.8 


16.0 


• 36S 

20 9 


3-63^ 


3IO 
327 


tRoo 


Free 


Cu. Ft. 

R.P.M. 

H.P. 


■ 247 


336 


5630 
732 
440 


8850 


X2700 

490 
.591 


17300 
420 
«35 


32600 
368 
1.76 


38600 

3#> 

2.32 


35200 

294 


51000 
245 
3 97 


69000 

210 

S V) 


90200 
'8s 
7 0.1 


114000 141000 

.63 '48 
_ 8.90 U.q. 




Heater 


Hi. p. mT 

H. P. 


■.588 
I 05 


.368 
« 43 


1181 
1.87 


•954 
2 93 


801 

4:»3 


679 
$■75 


595 
7 SO 


" 526 

9 50 


483 
11.7 


r. 


354 
230 


■303 
300 


363 336 
38.0 47 


21J0O 


Free 


Cu. Ft. 

R. P. M. 

H.P. 


3S20 
.090 
■336 


4800 
III 


6280 
81S 
•597 


9800 
655 
931 


14126 
545 
«.34 


'9*40 
470 
1.83 


35120 
4«b 

2.39 


3 02 


39260 
327 
3 73 


56510 
372 

i.38 


76960 
23i 
7 3> 


100520 
306 
9 55 


127200 
182 
12 1 


.57.00 
.64 

'49 




Heater 


R. P; M. 
H. P. 


1764 
1.30 


1520 

••77 


1312 
2.30 


3.60 


890 
5 15 


755 
TOS 


664 
925 


585 
1. 7 


528 
'4 5 


,t% 


.t. 


336 
37 


293 26a 
46.8 578 


2200 


Free 


Cu.Ft. 

R. P M- 

H P. 


.3890 
1200 
424 


4300 
1&50 
57« 


6800 
900 
•754 


.0800 


1.70 


21130 
515 
2.31 


37600 
.450 

.3^02 


35000 

400 
3.82 


•43200 
360 
4 72 


62200 
300 
679 


84700 
257 
9-25 


110500 

328 
13 I 


139800 
ao3 
«5 3 


173500 




Heater 


R P.M. 
H. P, 


.94.0 
\ 1 . 70 . 


.1700 

a. 30 


1460 
300 


1163 


6'i: 


830 
92s 


727 

. 12 I 


64s 
'S3 


,1^8 


485 
27 


4' 5 

37 


4^^ 


61.0 


& 



128 Notes on Heating and Ventilation 

Example. — As an example of the fan system consider 
an auditorium. The dimensions of the room are 40 feet 

9 inches by 79 feet 6 inches by 127 feet 9 inches. The 
volume of the room is 444^330 cubic feet. It has 203 
square feet of glass surface and 5,441 square feet of wall 
surface. The heat lost from the room, figuring in the 
same way as we have for previous examples, will be 168,- 

010 B. T. U's. The hall has a seating capacity of 2,500 
persons. Allowing 2,000 cubic feet of air per person, the 
necessary air to be admitted to the room will be 5,000,- 
000 cubic feet of air per hour. This equals 383,000 
pounds. In order to heat the room with this quantity of 
air entering, it will be necessary to heat the air but a 
fraction of a degree so that the air admitted to the room 
for ventilating purposes will be far more than that neces- 
sary for heating purposes. It is best, then, to figure on 
admitting air only for purposes of ventilation. To heat 
this air from zero to 70° would require 383,000X.2375X70 
=6,353,000 B. T. U's. Eef erring to Table 27, we see 
that a heater coil 12 pipes deep will heat air having a 
velocity of 1,250 feet per minute to a tem.perature of 82°, 
which is probably about the proper assumption to make 
in this case. The coil will condense 2.1 pounds of 
steam per square foot per hour. Each pound gives 
up about 970 heat units, so that each square foot of 
heater coil will give off about 2,000 B. T. U^s per hour. 
Then the number of square feet of heater coil required 
would be 6,350,000-^2,000=3,175 square feet. The heater 
coils are usually made of 1-inch pipe and each square foot 
of surface is equivalent to about 3 feet of 1-inch heater 
pipe, hence there will be required 3,175X3 or 9,525 feet 
of 1-inch pipe in the heater coils. The air to be admitted 
to the hall is 6,350,000 cubic feet per hour or 106,000 feet 
per minute. The usual velocity allowed for the air pass- 
ing through the heater coil is 1,200 feet per minute. This 
will require an air area in the heater coil of 106,000-^ 
1,200=88 square feet. The area in the various heater 
coils will be found in the blower company's catalogues 



Notes on Heating and Ventilation 129 

and is also given in Table XXVIII. This will determine 
the size of the heater coil to be used. 

On account of the size of the hall and the amount of 
air introduced, it will be best to have two fans for deliv- 
ering air into the building. Each fan would then need a 
capacity of 53,000 cubic feet per minute. In order to 
overcome the resistance of the flues the pressure should 
be from .2 to .3 of an ounce at least. From the table of 
fan capacities we see that a 200-inch fan running at 125 
revolutions would require 19.3 horsepowers and produce 
a pressure of .435 ounces. This, however, is a little higher 
pressure than would be desired unless the flues were quite 
long and had a number of curves. If the flues are short 
and straight we could use two 220-inch fans running at 
100 revolutions. These fans would deliver 55,000 cubic 
feet of air each, with a pressure of .335 ounce and require 
17.1 horsepower to drive them. By using a larger size of 
fan 2.2 horsepowers for each one of the fans would be 
saved. Assuming the air to be delivered to the hall by 
four ducts, these ducts being large, it would be reason- 
able to allow a velocity of 1,500 feet per minute in the 
duct. Each duct would have to carry 26,000 cubic feet of 
air per minute; 26,000-^1,500=17.3 square feet in area. 
As the registers of these ducts will be large and situated 
well above the head line, it would be safe to allow a 
velocity of 500 feet per minute to the register. The area 
of each register, assuming that there are four, entering 
the room, would be 52 square feet. The vent flues leaving 
the room should have an area about equal to the hot air 
flues. 



130 Memoranda 



C H A P T E R VIII. 

A CENTRAL HEATING SYSTEM. 

It is not intended in this chapter to discuss the design 
of heating systems, such as is used in the heating of a 
city, but systems that are in use for the heating of public 
institutions, or groups of build- 
ings. The type of system to be Design and Location. 
used in a given installation de- 
pends very largely upon the location and character of the 
buildings to be heated. No two systems, even though 
designed by the same engineer, will be the same and the 
suggestions made in this chapter can be but general. 

Before starting the design of a central heating system 
it is first necessary to have a careful survey of the prop- 
erty. This survey should show the exact location of the 
buildings to be heated, the elevation of the basement and 
first floor, together with a general profile of the ground 
through which the tunnels or pipes are to be run. The 
profile of the ground will largely decide the proper loca- 
tion of the power house. The power house should be 
located as nearly as possible to the buildings to be heated 
or as near as possible to the largest steam load. It should 
be low enough, if the profile of the land will permit, so 
that the condensation of the return mains may be re- 
turned to the power house by gravity. If possible, it 
should be so located that the floor of the boiler room may 
be drained to the sewer. Considerable difficulty is usually 
experienced to carry away the water, which results from 
the cleaning and blowing off of the boilers if no sewer 
connection can be made. The question of the soil, the 
location of the railroad siding, the water supply and the 
general appearance of the power house must also be taken 
into consideration. 

Before designing the power house the type and general 
form of boilers must be determined. If the power house 



132 Notes on Heating and V^entilation 

is to work on a low pressure system with a pressure under 
100 pounds, either fire or water tube boilers 
Boilers. may be used. In general, for this service fire 
tube boilers are very satisfactory, as they have 
large water storage, repairs are easily made, and the 
boiler may be crowded considerably beyond its rating. 
The economy of water tube and fire tube boilers is prac- 
tically the same. 

The principal objection to fire tube boilers," except of 
the Scotch marine type, is the large space which it occu- 
pies. If the power house is to be operated on a high 
pressure, that is, over 100 or 125 pounds, then only water 
tube or Scotch marine boilers can be used. The size of 
the boiler must be determined by the amount of steam 
which is to be used by the radiation and other devices 
taking steam from the boilers. The steam used by the 
different forms of radiation can be determined by refer- 
ence to the rauiator tables previously given. After hav- 
ing once determined the quantity of steam the plant is 
expected to use, it is customary to assume that each 
square foot of heating surface in a boiler will evaporate 
about three pounds of water. This determines the total 
amount of heating surface that the boilers should contain. 
The boiler units should be so selected that one boiler or 
one set of boilers will take care of the plant during the 
light load period of operation, that two boilers or sets of 
boilers will take care of the average operating load. In 
addition to this, there should be a boiler or set of boilers 
that will take care of the maxim^um conditions of load. 
There should always be a sufficient number of boilers in 
the plant so that at least one boiler or set of boilers can 
be out of service for a considerable period of time for 
cleaning or repairing. In a central heating plant using 
the gravity return system, it is necessary that all boilers 
have their water line at the same level. 

Systems of Distribution. 

The general design of a piping system and its location 
will depend upon the system of distribution adopted. 



I 



Notes on Heating and Ventilation 133 

If the gravity return system is used no main feed 
pump is necessary, the water returning 
by gravity, to the boiler, as previously Gravity System, 
described. With this system any dif- 
ference in pressure between that in the boiler and that 
at the extreme point in the piping system will result in a 
corresponding elevation of the water level in the return 
system at the extreme point — each one pound drop of 
pressure in the steam piping corresponds to an increase in 
the level of the water in the return piping of- 2.30 feet. 
It is essential, then, that the gravity return system with 
a difference in pressure between that at the boiler and 
that at the extreme point of the piping system be com- 
paratively small. 

The difference of pressure assumed will determine the 
size of the piping. In gravity systems it is usual to allow 
for the drop of pressure not over two pounds between the 
boiler and the extreme end of the system. 

In some cases, the gravity return system has been used 
over quite an extended area, the most distant building 
heated being as far as 2,500 feet from the boiler, and the 
system has given very good satisfaction. 

In a central heating plant using the gravity return sys- 
tem unless the steam mains are six to eight feet above the 
return it is necessary that the steam condensed in the 
mains be dripped separately from the main returns in the 
building and this drip pumped back to the boilers, prefer- 
ably by a pump and receiver, or some other mechanical 
means, such as return trap. This pump and receiver 
should be of sufficient size to take care of the steam con- 
densed in the mains when the steam is being turned on 
and the condensation is excessive. By returning the con- 
densation of the mains separately, excessive hammering is 
avoided and the system can be started much more rapidly. 
Gravity return is used only where the boiler pressure does 
not exceed ten pounds. 

The high pressure heating system is being little used for 
general heating purposes. It has some advantage?.. The 



134 Notes on Heating and Ventilation 

pipes are smaller and radiation is more effective per 

square foot. The .disadvantages, 
High Pressure System. however, outweigh the advan- 
tages in most cases. In the 
high pressure system cast iron radiators are not safe, as 
they are not usually made to operate at a pressure to ex- 
ceed twenty pounds. The pipe coil or other form of radi- 
ation must be used. The cost of producing steam, the 
chance of accident, and the cost of repairs are increased. 
It is not possible to use exhaust steam with a high press- 




Figure 28. 



ure system. When pipe coil radiation is used it would be 
safe to carry a pressure up to 100 pounds. In determining 
the size of steam mains for such a system a larger loss 
or fifteen pounds would not be considered excessive. In 
the high pressure system each building usually sends its 
condensation back to the return system through a trap 
so that the pressure on the return is only slightly above 



Notes on Heating and Ventilation 135 

the atmosphere. This condensation returns to a surge 
tank from which the feed pumps return it back to the 
boilers. The drip from the steam mains is dripped 
directly back into the return system. 

In a very large system where it is difficult to get 
enough difference in elevation between steam and return 
mains, or where the drop in pressure exceeds two pounds, 
it is usual to install some form of 

pump return. One of the most Low Pressure Pump 
common forms of pump return is Return System. 

to trap the return condensation of 

each building into the return main which carries the re- 
turn back to the boiler room. From this surge tank the 
water is returned to the boiler by means of a pump. The 
drip from the steam main is trapped directly to the re- 
turn main. The most objectionable feature of this system 
is the constant attendance and the repairs necessary to 
take care of the traps. 

In most cases the heating system is combined with 
some form of power system. This makes a very econom- 
ical combination as the exhaust 

from the power plant may be used Combination of power 
in the heating system. Where and heating system, 
the exhaust can be entirely 

utilized for from six to eight months of the year it is 
seldom profitable to use condensing engines. 

There are two general schemes used for combining a 
power and heating system. In the simplest form the boil- 
ers are operated at a high pressure. The steam goes from 
the boilers to the engine, and after the steam leaves the 
engine it passes directly to the heating system. A by- 
pass pipe is carried from the high pressure steam main to 
the heating main and in this by-pass is located a reduc- 
ing pressure valve. If for any reason the engine does 
not supply sufficient steam to maintain pressure on the 
heating system, then the reducing valve opens and intro- 
duces live steam. The returns from the heating system 
are carried back to the boiler by means of a pump. 



136 



Notes on Heating and Ventilation 



Fig. 28 shows the general arrangement of systems of 
this kind with a by-pass for furnishing live steam to a 
heating system. This system depends in a measure for 
its success upon the action of the reducing pressure valve. 
Such valves, however, have been found to be quite re- 
liable when well designed and well made. The principal 
cause for trouble is when the valve becomes foul with 
dirt. In a system of this kind the engine exhaust is 
always provided with a back pressure valve connected 
to the atmosphere. This valve is so arranged that if for 







Figure 29. 

any reason excessive pressure should accumulate in the 
heating system the valve would open and exhaust the 
steam into the atmosphere. The arrangement shown in 
Fig. 28 is most used in small plants and both the heat 
and the power can be taken from one boiler. In larger 
plants the heating boilers are operated on the low pres- 
sure and the power boilers on the high pressure system. 
In the high pressure system steam goes to the engine and 
pumps and is exhausted through an oil separator into the 



Notes on Heating and Ventilation 137 

low pressure system. The pressure of the exhaust is de- 
termined by the pressure carried on the low pressure sys- 
tem. This system is particularly desirable where the 
heating load is considerably larger than the power load; 
and where at times the engines are entirely shut down 
and only the low pressure system is operated. Fig. 29 
shows a sketch of this arrangement. 

In carrying pipes from one building to another it is 
always desirable, if possible, to carry them under ground. 
Carrying underground affords 

much better heat insulation, the Method of Carrying 
pipes are more easily supported Pipes. 

and are less apt to be disturbed. The simplest method of 
underground distribution and the cheapest is to enclose 
the pipes in a pine board case, as shown in Fig. 30. This 




^/ei/cj/'''on 



r/cn 



Figure 30. 



arrangement,, however, is not a desirable one, as the 
boards soon rot out, the heat insulation is not satisfactory 
and the pipes are very difficult to get at for repairs. Its 
chief recommendation is that it is cheap. In most cases 
it should be used only for temporary work. 

A system quite largely used is to enclose pipes in pump 
logs, that is, hollow wooden pipes. These pipes are 
creosoted and filled with an asphalt paint or some other 
means of preservation. They are often lined with tin or 
some other form of metal lining. The pipe is passed 
through the pump log and is usually covered with about 
one inch cf some standard form of pipe covering. This 
method of running the pipes furnishes quite satisfactory 



138 Notes on Heating and Ventilation 



heat insulation. It is much more durable than the pine 
board duct, it is easier to install and easier to replace in 
case of repairs. It has, however, the disadvantage of 
making the pipe quite inaccessible and in case of accident 
the removal of the entire system is necessary; this in 
many places is very expensive. The builders of one of 
these pipe ducts stated that the loss in the pipes enclosed 
in this manner is from one-fourth of one per cent to six 
per cent per mile of pipe delivering steam at its full ca- 
pacity. The larger the pipe the smaller the proportional 
heat loss. Fig. 31 shows a cross section of a pipe log 
with covering. This pipe log construction is most used in 



T/'n l/ntn^ 





t/et/^/'/ 



t/^//0/7 



P/c 



Figure 31. 



central heating systems for building connections and 
where only one pipe is to be used in supplying the build- 
ing. 

Where it is necessary to run a number of pipes the most 
desirable method is to run through tunnels made of brick 
or cement. The size and form of tunnel used will de- 
pend upon the number of pipes to be carried, the charac- 
ter of the soil and the depth into the ground. Where 
tunnel s^^stems have been installed the general experience 
has been that they more than paid for themselves in a 
short time, as they entirely do away with the necessity of 
taking up the pipe and allow for repairs and frequent in- 
spection. Fig. 32 shows a small sized tunnel. This tun- 
nel has been used for carrying pipes not over 8 inches in 



Notes on Heating and Ventilation 



139 



diameter. The tunnel is 3 feet 6 inches wide, 4 feet 6 
inches high. It is made of brick 4 inches thick with one 
inch of Portland cement outside. This cement is painted 
a thick coat of tar or asphalt to below the crown of the 
arch. Wherever the supports come the tunnel is ribbed 




Figure 32. 



with an 8-inch rib of brick 16 inches wide. This rib is 
placed about every 10 feet. A tunnel of this kind has 
been in use for some time and has given good satisfac- 
tion. It is not desirable to use this sort of tunnel for 
large pipe or where the tunnels are to be frequently in- 
spected. 



140 Notes on Heating and Ventilation 

For larger pipes the section shown in Fig. 33 is much 
more desirable. This tunnel is 5 feet by 6 feet inside di- 
mensions. The tunnel is made of two courses of brick or 
about 9 inches thick. It is plastered on the outside with 
one inch of cement and then tarred down to the crown of 
the arch. At the lowest point of the tunnel on each side 
is shown a 3-inch tile, which serves to carry away the 
drainage around the tunnel. If possible, this 3-inch tile 
should be brought to some drain. In moist clay soils it is 
sometimes found necessary to run a tile under the mid- 
dle of the tunnel connecting with the inside of the tun- 
nel so that seepage through the tunnel walls may be car- 
ried off either to the sewer or to the pumping plant. In 
saud and in clay soils this is not necessary, as almost no 
difficulty would be experienced from leakage. Fig. 34 
shows a tunnel made for carrying two large pipes. The 
tunnel is 5 feet 6 inches by 6 feet 6 inches and gives am- 
ple passage way between the pipe supports for easy access 
at ail times. 

The cost of tunnels depends upon the nature of the 
excavation and the price of materials. To give an ap- 
proximate idea of what tunnels cost, the tunnel shown in 
Fig. 32 has been constructed, including excavation, back 
filling and all necessary material, for $3 per linear foot. 
The tunnel shown in Fig. 33 has been constructed for $5 
per linear foot and the tunnel shown in Fig. 34 has been 
constructed for $5.50 per linear foot. 

The size of the pipe necessary to carry a given quan- 
tity of steam is determined by the allowable loss of 

pressure that the system will per- 
Sizes of Pipes. mit. In a low pressure system 
this loss of pressure should not 
exceed two pounds. In a high pressure system it should 
not exceed 10 pounds. The rule most commonly used is 
called Babcock's rule, and is as follows: Multiply the al- 
lowable drop in pressure by the weight of steam per cubic 
foot, as given in the steam tables, multiplying this prod- 
uct by the fifth power of the diam.eter and divide the re- 



Notes on Heating and Ventilation 



141 



suit by. the length of the pipe, multiply by one plus 3.6 
divided by the diameter of the pipe. Take the square 




Figure 33. 



root of the result and multiply by 87. The final result ob- 
tained will be the weight of the steam which the pipe will 
carry per minute with the given drop in pressure. 



142 



Notes on Heating and Ventilation 



The best way of handling this expression is to assume 
different diameters of pipe and then try a number of 
standard pipe sizes. In this way determine the pipe 




Figure 34. 



size which approximates most closely the weight of steam 
which it is desired to carry. 

In low pressure systems the return main is usually taken 
as one-half the pipe size of the steam main up to 10 inches. 
Above 10 inches the size is taken as one-half the size of 



Notes on Heating and Ventilation 143 

the steam main minus one size. As, for example, a 10-inch 
main would require 5-inch return, a 14-inch would require 
a 6-inch return. The size of drip main for a given steam 
main depends entirely upon the length of the main. It 
should never be less than % inch and it is seldom neces- 
sary to make the pipe over % inch. A 1%-inch drip main 
will take care of 2,000 feet of 12-inch pipe providing 
the pipe is well covered with standard covering. 

When pipes are carried through tunnels it is necessary 
to provide a different form of hanger than in building 
work. In tunnel work the head 

room is so limited it is ordinarily Hangers and Anchors. 
impossible to suspend pipes from 

above and they must have some form of roller hanger. 
Fig. 34 shows ball-bearing hangers for 12-inch pipe and 
roller hangers for the 6-inch pipe. Fig. 32 shows a very 
simple form of roller hanger. Fig. 33 also shows a form 
of ball-bearing hanger for 8-inch pipe and roller bearing 
for 4-inch pipe. The ball-bearing hangers shown in these 
figures have given very satisfactory results. They are 
expensive, but the expense is warranted. In tunnel work 
the clearance is so small that it is necessary to know ex- 
actly where the expansion is to be taken up. The only 
way to be certain of this is to anchor the pipe at the 
point desired. These anchors are usually made of heavy 
cast iron with wrought iron straps enclosing the pipe. The 
hangers should be built into the tunnel or building walls 
and should pass entirely through the wall, projecting 
4 inches or more on the opposite side of the wall. The 
anchors should not be built into walls that are less than 
12 inches thick, and preferably they should be 16 inches 
thick. Tn putting in hangers and supports in tunnel work 
it is a very important thing to see that a clear space is 
left through the center of the tunnel which will give easy 
access to the tunnel. The easier the access and the more 
comfortable the tunnel for passage, the more frequent will 
be the inspections, and such inspections insure of the pip- 
ing being kept in the best possible condition. 



144 Memoranda 



6 HA P 1 E R IX, 

PIPING, COVERING AND OTHER APPLIANCES. 

In all piping installation it is customary to cover the 
distributing pipes, except radiator connections. It is 
good practice to cover the risers passing through build- 
ings, together with all steam and re- 
turn mains. Where the water mains Pipe Covering, 
pass through rooms in which any drip 
from the pipes would be objectionable, such pipes are also 
covered to prevent the condensation of moisture on the 
outside of pipes. In general the best form of non-conduc- 
tor is dry air, which is so confined as to prevent circula- 
tion. In all successful forms of covering air is confined 
in the structure of the covering and the effectiveness of 
the covering depends largely upon the confining of this 
air. The effectiveness of different forms of covering was 
determined in a series of experiments made under the 
direction of Prof. M. E. Cooley, University of Michigan. 
Table 33 hows the relative effectiveness of some of the 
different forms of covering. 

The results of these tests show that hair felt is the best 
non-conductor. It is not, however, suited for over 10 
pounds pressure, as it chars and breaks down at higher 
pressure; this is also true of the wool felts. In low- 
pressure work at such temperatures as are ordinarily 
used, it is found to be quite satisfactory. It is expensive, 
but its expense is warranted in the saving from conden- 
sation in the piping. 

Table 84 shows the relative effectiveness of different 
thicknesses of covering. Column 3 of this table shows the 
relative effectiveness of the various thicknesses of cover- 
ing compared with the bare pipe. From this table it is 
not a difficult matter to figure the amount of saving 
that may be made by using various thicknesses of cover- 



146 Notes on Heating and Ventilation 

ing. Knowing the amount of steam carried per year and 
the cost to produce 1,000 pounds of steam, and having the 
results shown in this table, we can easilj compute the 
financial saving to be made in the various thicknesses of 



Table XXXIII. 

Relative Value of Different Pipe Coverings. 

__ _ 

^i ^ .%. St3 8 If ^"3 

1. Asbestos 145 .319 1.23 136. .803 

2. Magnesia 119 .224 .94 166. .915 

3. Magnesia and asbestos. .125 .500 1.12 118. .879 

4. Asbestos and wool felt .190 .228 1.12 102. .910 

5. Wool felt 117 .234 1.16 110. .904 

6. Wool felt and iron with 

air space 134 .269 125. .828 

Sectional Coverings. 

7. Mineral wool 097 .193 .94 91. .952 

8. Asbestos sponge 105 .220 1.12 102. .920 

9. Asbestos felt 100 .217 1.35 94. .923 

10. Hair felt 080 .186 1.45 75. .960 

Non-Sectional Coverings. 
Two layers asbestos 

paper 388 .777 364. ,263 

Two layers asbestos 

pap^r, one inch hair 

felt and one thickness 

canvas 070 .150 68. 1,000 



covering. In doing this it is usually found that for build- 
ing work an inch covering is sufficiently heavy; but for 
tunnel work and all work where the heat loss from the 
pipe is entirely lost and does not enter the building it is 
economy to use covering as much as 2 inches thick. 
Table 35 shows the heat lost through a 1-inch wool 
covering with various steam pressures. In covering 
a piping system the fittings and valves should 



Notes on Heating and Ventilation 147 

be covered the same thickness as the pipe. This 
also applies to flanges and steam traps. Where flanges 
and other parts which require removal are covered they 
should be covered so that the covering can be taken off 
easily. A satisfactory method of doing this is to form 
a covering composed of one layer of asbestos paper, 
1 inch of hair felt and one thickness of 8-ounce duck. 
These are quilted together with cord so that the 
jacket is firmly held in one piece. This covering is 







Table XXXIV. 




Heat Transmission 


for Varying Thicknesses 


of Covering. 








Ratio of 


B. T. U.'s 




Condensation 


of condensa- 


trans- 


Thickness of 


per sq. ft. per 


tion covered 


mitted per 


covermg. 


hour 


in pounds. 


to bare pipe, sq 


. ft. per hour. 


1'^ 




.120 


.281 


167. 


% 




.117 


.255 


163. 


1 




.107 


.231 


149. 


IV2 




.099 


.219 


138. 


1% 




.087 


.191 


121. 


2 




.078 


.19 


108. 


The covering used in obtaining the above 


results was 


a wool felt. 











then fastened over the pipe to be covered by means of 
hooks and laces. The advantage of covering may be 
shown from the following computation: 

In a given steam plant it was found that the heat lost 
from bare pipes per hour was 3,355,000 B. T. U. In the 
particular plant in question the number of heat units 
required to make a pound of steam was 990 and this loss 
of heat would represent a condensation of 3,390 pounds 
of steam per hour. Assuming an evaporation of 9 pounds 
of steam per pound of coal this would be equivalent to 
376 pounds of coal per hour. If the plant were operated 
365 days in the year and 20 hours a day, and the coal 
cost $3.25 per ton the yearly loss would be $2,069. By 
covering the pipe 1 inch thick with hair felt the loss 



148 Notes on Heating and Ventilation 

which would result from the bare pipe would be reduced 
15%, or equals $314, making a saving of $1,755 by putting 
on covering. This amount capitalized at 10% would rep- 
resent an investment of $17,550, In the particular case in 
question the actual cost of the covering was but $3,500. 

Air valves should be placed on all high points on steam 
and return mains and at all points where air may accumu- 
late. The most satisfactory forms of air valves have been 

those using floats or some substance 
Air Valves. which has a large coefficient of expansion. 

In central heating systems there should be 
provided large air valves. The ordinary air valve used 
for radiators is not sufficient. A very satisfactory method 





Table XXXV. 




Heat Transmission for Varying Pressures. 1 






Ratio of 


B. T. U.'s 




Condensation 


condensation 


transmission 


Gauge 


per sq. 


of covered 


per sq. 


pressure. 


ft. per hour. 


to bare pipe. 


ft. per hour. 


5.3 


.108 


.239 


100. 


9.6 


.111 


.233 


104. 


15.5 


.126 


.227 


110. 


20.5 


.134 


.223 


119. 


28.7 


.149 


.230 


136. 


36.7 


.160 


.230 


146. 



is to attach to the high point of the steam main a % to 
%-inch pipe about 18 inches long, the end of which is 
closed by means of a valve. On this pipe is located two 
or three air valves of the ordinar^^ type. In installing 
the system the main valve in the pipe may be opened so 
as to allow the air to escape. As soon as steam comes 
from this valve it is closed and the small valve will take 
care of the ordinary accumulation of air which takes 
place. 

The pipe used in steam heating work is usually of 
standard weight, except for boiler blow-offs and boiler 



Notes on Heating and Ventilation 149 

feed pipes which are made of extra heavy pipe. 
Steam pipe is made of steel 

or wrought iron. Wrought pipg, Valves and Fittings, 
iron is more expensive than 

steel but gives better results. Steel pipe can be made 
which is very satisfactory, but care should be used in 
selecting a good grade of pipe. Cast iron elbows and tees 
are more satisfactory than malleable iron and they should 
be full weight. There are on the market light-weight cast 
iron fittings. The advantage of cast iron for fittings is 
that the fittings can be broken with a sledge if at any 
time it is desired to open the pipe. If malleable iron fit- 
tings are used it is necessary to cut them out with a cold 
chisel, which is expensive. In putting up piping 
bushings are to be avoided as much as possible and reduc- 
tion in size made in the fittings. 

Valves 2 inches and under are usually made of brass 
composition and should be of full weight. Over 2 inches 
it is customary to use iron body brass mounted. Valves 
over 4 inches should be provided with yokes. Valves 6 
inches and over should be provided with bye-passes. 

In almost all cases where exhaust steam is available it 
is economy to use it for heating purposes. This can easily 
be seen from an examination of the steam tables. To 
make steam at 100 pounds 

from feed water at 212° re- Exhaust Steam Heating, 
quires 1,012 B. T. U^s. To 

make steam at 5 pounds pressure from feed water at 212° 
requires 97 B. T. U's. To put it in another way, it re- 
quires 3.5% more heat to make steam at 100 pounds press- 
ure than at 5 pounds pressure. In passing through an 
engine, however, from 10% to 20% of the steam is con- 
densed, so that of the original heat given to the steam 
about 80% of it is available in the heating system. 
Where exhaust steam can be used, about 20% of the cost 
of the coal should be charged to the engine and 
about 80% to the heating system. In using exhaust 



150 Notes on Heating and Ventilation 

steam for heating purposes before entering the heating 
system the steam should be passed through a large sepa- 
rator to remove as much oil as possible from the steam, as 
shown in Figs. 28 and 29. It is always danger- 
ous to have oil returning to the boilers. The 
drip from the oil separator usually contains so much 
oil that it is advisaole to waste it. There is one other 
objection to the use of exhaust steam in that it brings 
additional back pressure upon the engine, the heating sys- 
tem usually being operated at 5 pounds pressure above the 
atmosphere. This difficulty can be overcome by the use 
of some form of vacuum heating system. 

There are two principal forms of vacuum heating sys- 
tems, one in which the air is drawn from the radiator air 
valve by means of an air pump, or aspirator, and in the 

other the radiator is fitted 
Vacuum Heating Systems. with a special form of return 

valve and the return system 
is placed under a vacuum by means of a pump or aspira- 
tor. The vacuum systems of heating lowers the tempera- 
ture in the radiator so that the radiators do not condense 
as much steam as they w^ould under full pressure. They 
do not make any material saving in the amount of coal 
burned by the system, but where exhaust steam is used 
they materially assist in reducing the back pressure on 
the engine. In most cases the back pressure on the 
engine does not affect seriously the economy of the en- 
gine, but only its capacity. 

Another advantage in the vacuum systems which is 
particularly true in hotels, hospitals and school buildings, 
is that it insures a definite circulation in the radiators 
independent of the steam pressure. The systems which 
carry off the air from the air valves do away with the 
objectionable odor which comes from the opening of the 
air valves in the steam system. 

Temperature regulation is a most desirable thing in 
most heating systems, particularly for public buildings. 



Notes on Heating and Ventilation 151 

In the better forms of temperature regulation reliable 
tests show that the room can 

be controlled within 3° of the Temperature Regulation, 
given temperature. This uni- 
form temperature adds very much to the comfort and 
health of the occupants of the room. In addition it rep- 
resents a saving of fuel. In buildings not provided with 
temperature regulation, as soon as the room becomes too 
warm the windows are opened and a great deal of heat is 
lost from the building. Where temperature regulation is 
provided windows are seldom opened in order to reduce 
the temperature. This makes a saving in some cases as 
high as 20% in the coal bill. The temperature regulating 
systems are expensive to install and require some attend- 
ance, but where the expense is warranted the installation 
of the temperature regulation system is always desirable. 

In the large cities the smoke and dust in the air makes 
it very undesirable to introduce this air into rooms for 
ventilating purposes. In order to avoid this there have 
been devised a number of systems which 
wash the air. The general principle in Air Washers, 
all these systems is to pass the air 
through sheets or sprays of water. After having passed 
through these sheets of water the air is passed through an 
eliminating device by which the excess of water in the air 
is removed. Previous to passing through the air washer 
the air should pass through tempering coils unless it is 
sufficiently warm so that there is no danger of freezing 
the water. After having been washed it is then passed 
through the heating coils. In connection with the air 
washer there is often introduced a system for cooling the 
air. The air can be cooled in the washer itself to 
within 5° of the temperature of the cooling water enter- 
ing the washer. In locations where cold water is avail- 
able for washing the air it is not necessary to have a 
cooling system. Where cold water is not available then a 
refrigerating plant should be introduced and the water 
cooled by means of the refrigerating plant. Another 



n 



152 Notes on Heating and Ventilation 

method is to introduce pipes in the current of air through 
which is circulated cold brine from a refrigerating ma- 
chine. The air washing devices when properly installed 
are very effective in removing dirt and the amount of 
dirt removed is surprising. In the case of a certain build- 
ing the amount of dirt removed from the air washer is 
about two wagon loads per week. 

In addition to the systems that have already been 
mentioned there have been used with considerable success 
a system in which the exhaust steam from the engine 

passes into a large hot water 

Combined Hot Water and heater. The hot water from 

Exhaust Steam System. this heater is circulated by 

means of a centrifugal pump 
through a hot water heating system. This system has the 
advantage that it does not increase the back pressure on 
the engines and the circulation in the hot water system is 
positive, as it is produced by means of a pump. It does 
away with any trouble that might arise from oil getting 
into the boilers and it allows of the water being carried 
for a longer distance. The pump and heater add addi- 
tional mechanism to the system and means must be pro-" 
vided for operating the pump. 



p 



km 13 1fc06 



